Yeh thats right cheif, its a series of compounds by Farecla, G3 being the coarsest, G6 medium, and G10 is the finishing/polishing compound. Its the gear i was 'trained' on at work, so tbh ive just stuck with it. I always follow G3 with a finishing compound personally on any colour, but its imperative on solid and dark colours or it'll leave them streaky and swirly as hell and looking awful as its quite aggresive, especially if the buffer speed is too high.
Ive no paint depth reader im afraid no, nothing that technical lol.
Ive had a session on the vehicle today in the workshop though, gave it a wash down then started off as you reccomended with the medium compound on a medium head on the buffer, no pigment at all came off on the pad, other than from the 'patch' where the laquer appears to have rubbed through on the rear quarter i mentioned previously. Anyhow, i went over the whole car, and there was a slight improvement but nothing exceptional. So i went hell for leather and hit it with the coarse G3 over the entire car, and followed it up with a soft head and the G10 polishing compound, then a dose of AutoGlym Super Resin Polish, finished off with AG Radiant Wax. Its definately improved the finish, obviously the marks/scratches and fallout has all been removed and the paint is now glass like and beatifully shiny, but still not back to full red but to be honest i'm probably expecting too much of paintwork on a 15 year old car to come up much better than it is now!

I appreciate this is fairly useless without pics, i forgot to take the bloody camera to work, so ill get some up as soon as the rain breaks long enough to allow me to get some taken!