Hi Steve, glad to hear you like wfp!
Personally I always clean the frames, as others suggest on a first clean do frames and glass (paying more attention to frames to get rid of all the muck/soap residue) leave to dry and go back and clean glass only and giving it a good rinse, as for brush on or off, with sheeting glass I rinse on, as for coated glass or the beading type I tend to rinse off just to make sure, be aware though of rising off that you don't spray dirt and contaminates onto the glass from surrounding brick work, foliage etc.
Rinsing on though imo is preferable, and a good brush that does'nt hold the dirt will make this a lot easier.
I dont know what system you are using but if you arent already I would strongly recommend microbore hose and a flow controller tap on the end of it, these two things have vastly improved the efficiency of my work and save on my water usuage.
Hope this advice helps you sir.
Any other questions ask away.
Simon