Vaseline is pretty easy to apply, just open up your Rubik's cube (if you don't know how, you can just turn a layer of the Rubik's cube about 45 degrees, insert the back of a spoon [or any dull flat object] and pry the middle piece out) then smear a large quantity of Vaseline into the cube, like I said earlier, it isn't the best thing to lubricate your Rubik's cube with, but if it is the only thing around, it works. (Note that if you lubricate your Rubik's cube with Vaseline, adding silicone to it later will cause a chemical reaction that turns the Vaseline into super glue, no joke.)
