Don't discount grease in dusty dirty conditions, do your research.
Grease - Slide GLide, WeaponShield, Frog Lube? Mobil1 or Valvoline or Aeroshell
Oils - WeaponShield, AmsOil original, Mobil1, Militec-1 (no so hot for corrosion etc.....)
Hmmmm, seems one fits all.
I use mobile One in a spray.... you can Really get down in there....8)
jk, use q-tip type application