I have a friend that is a body man, and at their shop, they only use this stuff....They had a high end plastic welder, but all of the guys could make it work well. He said it did a sloppy job, and now that they have this stuff, the plastic welder is obsolete!
http://www.lord.com/Products-And-Solutions/Adhesives/Automotive-Repair-Adhesives/Product.xml/314
I have used it lots to repair cracked plastic, and even to make new plastic from parts that were broken, and pieces were missing!
Awesome stuff. It is expensive, the gun is expensive, and the tips that mix the product aren't cheap, but it's the best!
If you go to the products section of their website, all their products have online instructions on how to use all of their products, how long til set up, how long til you can sand, etc. , etc.!
Good luck!