I used to use ionics brushes. In my experience, the bristles are so dense the y hold dirt really really bad. Far worse than the vikans. Also they jets are big, so even if you use loads of water its actually quite low pressure and doesn't always push the dirt down the window effectivley. Your first move should be 2mm jets instead of 3mm. Next try out other brushes, you'll prefer almost all of them to your ionics brush, everyone my way seems to have ditched them. I reckon that's what your problem is.