Yeah, avoid devils castle, yuck. Snowbird under twin peaks is super easy access, if you take the tram. Gunsight at alta (thanks for letting me know) is probably easiest good hiking accessed patch. Other places in LCC have numerous patches, but require more hiking. Broads fork still has snow, although it's a decent hike in there. The motherload is of course Timp, but as you said, thats quite a hike. I still gotta get in my august turns, so i'll probably hit gunsight or broads fork this weekend.
Last year i did ski on new snow in sept on about 4-5" at alta. The year before I think we got 3-4" on sept 10th. The cold storms are creeping down already, snow Glacier Natl Park yesterday. I'd say new snow in sept is a decent bet, but you gotta use rock skis, and find some grass. Timp didnt melt out last year, and certainly wont come close this year.