Hi Chris and Dec,
Thanks for your questions
The PADI Technical Instructor rating is an entry level for PADI instructors wishes to go the Technical training route to become a full Tec Deep Instructors. It only qualify the Technical Instructor to teach Tec 40 (which is similar to Advanced nitrox with other training agencies). This allows the instructor to gradually build experience in teaching Technical course while working on the requirements of becoming a Tec Deep Instructor.
• Prerequisites:
1. Be a renewed PADI Open Water Scuba Instructor
2. Be a PADI Enriched Air Diver (or hold a qualifying certification from another organization)
3. Be a PADI Enriched Air Instructor, or have successfully completed a PADI Enriched Air Instructor Training course.
4. Be a PADI Deep Diver Specialty Instructor or have successfully completed a PADI Deep Diver Specialty Instructor Training course.
5. Have a minimum of 100 logged dives where at least 20 dives were made with enriched air nitrox, 25 dives were deeper than 18 meters and at least 15 dives were deeper than 30 meters.
The training itself does not qualify participants to Teach Tec 40 straight away. The following post requirements have to be met:
1. Be a renewed PADI Master Scuba Diver Trainer or PADI Instructor with a higher rating.
2. Be a PADI Enriched Air Instructor.
3. Be a PADI Deep Diver Specialty Instructor.
4. Be certified as a Tec 45 Diver or have a qualifying certification from another training organization. For the purposes of this level, a qualifying certification is one that qualifies you to make decompression dives to 45 metres using air, EANx and oxygen using double cylinder, open circuit scuba equipment.
5. Have a minimum of 20 stage decompression dives after completing all of the above, the instructor can submit the application and once authorized can only teach and certify Tec 40 divers.
Tec 40 divers are only qualified to:
• Use decompression software and dive computers to plan and make decompression dives with no more than 10 minutes of total decompression and not deeper than 40 metres/130 feet.
• Use a single cylinder of decompression gas with up to 50 present oxygen (EANx50) to add conservatism to the required decompression.
In order for the Technical instructor to become a full Tec Deep Instructor, the instructor needs to go through an extensive Tec Deep Instructor training. They also have to meet the following post requirements:
1. Be a renewed PADI Master Scuba Diver Trainer or PADI Instructor with a higher rating.
2. Be a PADI Enriched Air Instructor.
3. Be a PADI Deep Diver Specialty Instructor.
4. Be certified as a DSAT Tec 50 diver, or have a qualifying certification from another training organization. For the purposes of this level, a qualifying certification is certification for technical deep diving using air, enriched air and pure oxygen for decompression dives to at least 50 metres/ 165 feet. The PADI
5. Have assisted with at least one Tec 50 course or one Tec 45 course.
6. Have a minimum of 270 dives logged, with at least 25 stage decompression dives that had a maximum depth deeper than 40 metres/130 feet.
7. Have certified a total of ten or more PADI Deep Divers and/or PADI Enriched Air Divers. Any combination that totals ten is acceptable.
8. Have successfully completed the Tec Deep Instructor Standards Exam and Tec Deep Instructor Theory and Practical Application Exam.
9. Meet the peer review water skill requirements listed on the Tec Deep Instructor Application.
To answer your questions, an instructor cannot get certified as PADI Technical Instructor and be allowed to offer Tec 40 course in just a weekend or two. However instructors can start their training even if they never had diver technical training before, go over their diver level first & progress with their skills and experience. Only once they meet the course performance requirements and post requirements, they can apply for the certificate. I started offering TecRec course in Ireland late 2009. Few instructors managed to meet the Tec Deep Instructor requirements in an average of a year with several weekends of trianing and skill evaluations while diving on their fun dives with twinsets to practice skills and log dec dives. Some are still working on it and others decided to teach few Tec 40 courses before progressing to the next isntructor level. I have had great reports on few of them like Declan from Dec & Dive, Cillian from Scuba Dive West and there are a handful of them are due complete their requirements this season.
If you have any further questions, please contact me.
Firas

Am I right in saying that someone who has no Technical Diving experience can do a course over one weekend and become an instructor!!
If this is true it sounds worrying that I could go somewhere and do a course and be instructed by someone who has only a hand full of dives more than me. If someone said to me a year after I started to Tech Dive that I was qualified to bring in people to bring in someone and teach them I would have laughed, it would seam like the biggest task over load that I ever heard of.
I must have this wrong but if so just for curiosity does anyone know what is the prerequirments for a tech instructor is? But if that was the case I think next time I do a Tech course I will be checking the instructors log book to make sure he has the experiences not the other way around as ud expect 
Maybe its just me that would be worried going to 40m/ doing skills ect. for the first time with someone almost as green?

I am sure here respected instructor trainers like Firase would check to ensure there is a pre gained level that they are happy with but it would worrie me to think that something like this could happen