Hosmer Lake is good now and I had a customer tell me he saw a hatch of large grey mayflies and the fish were wild for the hatch. I wonder if he saw Grey Drakes? They hatch in huge numbers at Sparks Lake in August so it wouldn’t surprise me they would be around at Hosmer too. 
Callibaetis Nymphs continue to be great at Hosmer, and so do Red Ice Cream Cones. Black Double Bead nymphs, Scuds, Zebra Midges and Balanced Leeches (watermelon is often my #1 on this lake, but Vampire is a good one too)
It is never a bad idea to run an any patterns on the reed line in the lower lake and in the channel. It works. Also a Black X Caddis draws them to the dry fly. 
As we move in to the fall time, water boatman quickly become a big part of the menu, so now is a good time to add them to your box and watch for signs the fish could be focused on them. Boatman develop wings in the spring and fall, and soon they will take a flight. I will have look it up again, but I think its a mating flight.