Ok I have seen people say wish is a better way healing than moonlight but on my diamond my umbreon is lvl 100 and nvr got a chance to teach him wish and I dnt see any tm called wish in the guide book!?!
Find a male Togetic (or Togepi) and train it to level 28 where is learns Wish. Breed Togetic with a female Pikachu/Raichu to obtain a baby Pichu that knows Wish. keep breeding until you get a male Pichu. It's 50/50 so should only take a few eggs to get one. level it up a bit and keep it happy so that it evolves into Pikachu. Breed the male Wish Pikachu with a female Umbreon to get an Eevee knowing Wish. level up and evolve into Umbreon. http://pokemondb.net/mechanics/breeding
Wish for Umbreon is an egg moves, so it learn Wish by breeding! http://pokemondb.net/pokedex/umbreon
An easier way than the ones above is simply breed a female eevee evolution with a smeargle this can be used to teach any egg move to any pokemon in the ground egg group.