I've said it before and I'll say it again, learn to ollie a skateboard. Even just doing it a few hundred times if you have zero success, the mechanics and complexity of them will get into your brain properly. This is how I taught my buddy, he still can't ollie the skateboard to save his life but his snow oliies are infinitely better. I showed him how and then he just practiced for a couple weeks randomly on work breaks and shit.
There is a a ton of dynamic and unnatural movement in an ollie that you do not realize just from watching someone who knows how. This is why someone who doesn't know how looks so terribad trying.
this this this!!! attempting to ollie on a skateboard helped my ollie on a snowboard so much, as well as my landings on jumps. I would assume because of how sketchy landing on a skateboard can be (at least to me).
as far as the tarp in the backyard goes, i did the same thing as donutz back in the day. a wet tarp works well