i use a viking sill brush mac mac, ive been wondering latley about getting a fan jet in one of my brushes, what do you think?
Like you I don't clean the frames but for this method you have to make sure the top beading & ONLY the beading is clean, do not go above it or flick the bristles causing splashes to go above it. I've been using this method for 5 years & get a more reliable clean than doing the whole frame. You need to have patience in mastering the technique but IMO it's well worth it as you'll be quicker & first cleans arn't an issue! I would strongly advise you get a gardiners super-lite brush, flocked or mono' which ever you prefere, I use the dual trim mono'. You must have pencil jets. Obviousley, the lighter & stiffer your pole the better, again, I use a gardiners slx-carbon.
I'll try to explain this next (very important) bit as best I can-
You have to clean the top beading of the window with the tops of the bristles i.e. not the ends (tips). First put your brush on the glass & move it up & down a couple of times in the middle of the window. This will get water into the whole brush &, more importantly, into the top row of bristles. It's important to have the bristles either facing the glass at 90 degrees (flush on) or have the brush ever so sleightly pionting downwards. This will avoid any water going above the beading. I usualy butt the bristles up to the beading & bend them down against it. Now, with the brush in this position, move it from side to side, keeping a bit of pressure up against the beading, covering the whole width of the window enough times to give it a good clean. Then, clean the glass as normal BUT, don't go wild near the top of the glass as this may undo your good work & pass water over the beading. When done, push the brush up to the beading again (in the same fashion as before) & move it slowly across from one corner to the next to rinse the whole window. Depending on the window, at this point I sometimes lower the brush a couple of inches & lift it just off the glass & do an extra rinse. This is mainly for windows that bead badly.
You must not have a flow-rate of such that the water bounces off the glass & causes unnesesary splashing. 2mm pencil jets & a nice, gentle but sufficient flow is perfect. The reason for a good shaped, accurate, light brush should be obviouse now too. The super-lite is the tool & is perfect for sash windows too.
Also, if you have to do any georgian windows, you must scrub the window-bars (astragals) from side to side & not vertically, or you will splash the top frame.
As said, it takes care & patience to begin with but before long you'll be flying & the technique will come as second nature. Many believe you cannot be so accurate as to not clean the top frame, I prove them wrong every day!
Hope that helps, off for a bath now.