Start practicing the trick on the ground without the board on to help build muscle memory. Then strap the board on and do they movements again. Now try them while going down hill I know you will use an edge but now your doing it while moving. Then as mentioned take it to a small box. After all this you'll have like 100 reps of the motion before you hit the rail. Find a low rail to start as well
-I'm Slyder and I suffer from "Gummer Syndrome"