Request that a teaching assistant who is already employed by the district be in your full band rehearsal period. When 504 accommodations need to be followed, you can handle the situation in private and have the TA supervise the band class for a few minutes. Try this: PLAN AHEAD AND PRACTICE THIS BEFORE YOU NEED TO USE IT. Tell full band to find 2-3 measures that need individual practice on their own. All play at once. It's likely that no 2 students are playing the same measures. Sounds like CHAOS but it WILL work. Just make sure the TA is in the band room supervising and reminding. I've done this in the past. My students loved it. The appreciated that I trusted them to find those spots rather than me spoon feeding them. I always asked "Who fixed at least one spot?" Usually every one raises his/her hand. The entire band benefits. In an ensemble of 50 students the result is 50 fewer spots for you to fix during full band rehearsal. Give it a try.