Most of the $$ you pay is prep/labor. Paint should be polished to properly clean surface to accept coating. If you don't have gear you'll probably be into it at least $300-400 for material cost.
You will want decent microfiber towels for leveling the coating. Pearl weave work nicely for that, then follow up with a high GSM for final buffing.
Clean
Chemical and physical decontamination
Polish
IPA wipe
Coat
As far as brands Cquartz UK is probably easiest for a first timer.
My car has Cquartz UK and a layer of Cquartz SIC on-top. I'll never install just UK ever again after using those together.
Recently did this red GR with the same combo
