I used Absorbine Ultrashield ($25 for a quart spray can, look in the "horse" section) when I had a cow who broke her horn off and it was crawling with maggots too.. ONE heavy dose of that and she was healed.
I'd use it at full strength for this kind of treatment (it lasts up to 3 weeks), but it can be diluted down to 25% and still be very effective for ordinary fly control.
I'd hold off on the LA200 for a bit.. Keep it handy, but some iodine may not hurt.
Maggots actually help remove the dead tissue.. for a time they can be beneficial by doing the cleaning without damaging healthy tissue, but not forever (IMHO)...
Spray them, wait a half a day, clean wound with peroxide then iodine, spray Ultrashield over it once more to prevent more flies.. it should heal up quickly.
I had a heifer just have a cesarian, it's fly season, once a week I sprayed her down, flies haven't touched the cut.