Indoor drills are hard in MN since most ranges prohibit rapid fire. Without being able to do even a basic bill drill, I have been focusing on running transition drills. I'll put up four targets and shoot one shot, move to the next target, and fire another shot. I start slow and then see how fast I can move from one target to the next at a constant speed.
Once I get moving too fast, I move the target array farther down range and keep going.