Are bees like other stinging insects, and can't really fly at night? If so, maybe try removing the cover when it's dark, then soaking them. Just a shot in the "dark".
John and Rebecca Dickson
Emma-7 / Little John-5 / Iva-1
Full Timing Again, Rev B
2013 Ford F-350 Lariat CC LB PSD
2015 SOB TT - With OC's Awning Poles (#8)
At least in Heaven, RVs will be perfect, and I won't have to keep fixing them.