The areas you mentioned are pretty limited for boondock opportunities. Near Dillon, is Clark Canyon Reservoir. Several Bureau of Reclamation campgrounds that are FREE, but not boondocking really. Missoula and Flathead Lake aren't really close enough to NF lands to make boondocking practical. Haven't found any old logging roads that are suitable for boondocking, and as stated, closer to town is private land. We live a few hours away and are still looking for decent places as well. Sorry can't be more helpful. Maybe other locals will chime in.