I've always used Tiger seal or Granville PU and they have lasted over 20 years for sure, tried some of the cheaper ones on occasion and found them not as good
Gravitex is single pack, Raptor is 2 pack, raptor will be tougher.
For years I used 3 coats of lechlar epoxy followed by 2-3 coats of gravitex and never had any problems but these days prefer the Raptor as it's a bit tougher
I've had a Bosch set for a few years and they are pretty good but not great on stainless.
For stainless I use Milwaukee or Starret.
Another good make is Morse also, they hold up on most materials really well
I use TORCO MPZ OR RED LINE ASSEMBLY LUBE or LUCAS OIL, most of the performance engine builders I know use these makes, these will stay stuck to the surfaces until you start the motor then will go into the engine oil and just provide added protection
I just use 2 pieces of tube with a fish mouth on each end that slide inside each other as a measure, hold in position and tape to hold if you see what I mean then cut to suit