I greased my Hi stop coaster hub like a boat axle, and for the first couple days, it didn't have quite as much power. Then it was fine. If it is assembled correctly, and your cones are adjusted correctly (the wheel should not have "clunk clunk" amount of play when the wheel is bolted in the frame, but shouldn't be grinding the bearing balls either), you should be able to clear out the grease quickly by just riding the brake under power for a little bit till you feel it pull.
You can buy V Brake bosses for about $1-2 each at major online bike shops, and have them welded to your frame (if it is steel, use steel. If it is aluminum, use a BMX plate adapter, or make sure you get Aluminum bosses, the pegs that V brakes screw onto.)
You can get a whole new wheel with a 12guages 36 spoke Downhill rim and Hi stop coaster brake for $30-40 from niagracycle.com. I love mine. It was black on black with silver spokes, and the motor cog fits right on if you take the dust cap off. You can install the dust cap back over the cog by pressing it a little flatter and greasing it a little. Works for me for about 400mi now.