where would one actually spray GT-85?
It's a vital part of any cyclist's toolkit IMO! GT85 is a light lube that dries to leave a PTFE (Teflon) protective layer. It contains a solvent which means it's also good to use wet as a light cleaner.
I use it to spray onto the cassette when I've cleaned it to get rid of any remaining water. I use it to lubricate the jockey wheels and sprung sections of the mechs. I also use it sprayed direct onto a really gritty chain and wiped off before employing the "Mickle Method".
My MTB is matt black anodised, and a wipe down of the frame tubing with GT85 makes it look and smell wonderful. It leaves a semi-gloss finish on cable outers and brake hoses.
I also use a squirt on the saddle clamp, the Seatclamp QR, the brake lever pivots, and the straw gets into the shifters to drive out any moisture after a wet ride or hose wash. I also spray it onto the pedal mechanisms
In fact, apart from the brakes and rotors every metal surface on the bike will benefit.