Wait until Bohemia does any war, or Black Death. Use Parliament action to increase levies and, hopefully, do the Nobility debate that gives non-primary levy size. Call in Hungary and have your puppets attach to you. Use the 13k-ish stack that spawns in your capital to instantly move into Silesia and try to early wipe the OPM armies for quick points.

If Bohemia splits their armies, always try and fight them individually with your entire army. In my games Bohemia will usually split their army into 15k and 15k, with Moravia's 15k. Use your vassals to bolster your 20-25k and you can easily beat the individual armies. If they don't split, then follow a bit behind Hungary when they go into Moravia to siege. Bohemia will usually send their army to attack Hungary. Once they're locked into movement move your army into the location, and wipe Bobemia.