i spray mine with waste oil twice a year,, last year even treated it to brand new oil...lol
Normally once in Spring and then once as we go into shooting season and it gets all wet and slubby
I swing it off the telehandler and steam clean the crap out of it
let it dry for a couple of days on the ramp, then give it a good spray with oil, normally have to mix it withy a splash of diesel to make it flow in the gun.
Then leave it to dry for several days...
TOP TIP
Don't do it two days before your MOT,, my tester is a mate and even he had a sense of humour failure when i made that mistake.....lol