Im just about to service my front fox fork i dont have the money to service my rear shock fully atm an wondered if its ok for me to simply unscrew the air can an add a couple of ml of float fluid just to keep things lubed up in there til i can purchase the seal kit an full service the rear shock?

Yeah that’s fine. How old is the shock? If it’s relatively new and doesn’t have any specific problems (leaking fluid, losing air) then an air can service is probably all it needs.

Let all the air out first 😉

I think fox recomend a 50 hr oil service or similar, which is pretty much what you describe, remove air can clean put float fluid back in, good to go! It’s what I do anyway.