It is very easy to mar the chrome on your Grex when using serated tools
When you strip the Grex please not the following:
1. Place a paper towel over or some other suitable material over the slider spring casing and if using a serrated lock wrench (vice-grip) align the teeth with groves of the slider casing (Part 13) and gently apply pressure. This only need be done once. After that use a flat adjustable spanner to tighten. I firmly finger tighten this part. Id does not need more than that. The first time you strip the TGi this is particularly tight because of the factory assembly.
2. Take care and place a paper towel or some other protection on bottom flat part of the airbrush assemble (see Full dis-assembly video at 1:56). This will be a little tight the first time and you don’t want the wrench scratching the surface.
3. As mentioned before I like to put a thin layer of silicon lube on part 18 so the airbrush air valve is not running dry.
4. I asked Danny to send a replacement locking screw on the underside of the airbrush. (dis-assembly video @ 3:00 min) you must use the correct size Philips or you will strip the head. Do not try and use a flat or Pozi style screwdriver). The screw is small and it is handy to have a spare.
5. Last – DON NOT and I say again DO NOT remove the front of the body. This is factory sealed with lock tight sealant and if you break the seal you will need to send the airbrush to Grex. The only part that you need to remove is the nozzle cap to change the fluid nozzle (Parts 2 and 3) Use the supplied wrench for this.
I hope that has helped.
Bryant Dunbar from Grex does a step-by-step video here