Tried the gardiners scraper and didn't get on with it. I'd find it would get in the way on a lot of my jobs and wasn't something I could keep on the brush/gooseneck all the time. Too much faff to add or remove.
I found glueing thin strips of non scratch scourer or the rougher side of velcro on to the ends of the stock very handy for stubborn birds mess or little yellow bug spots. As gardiner brush stocks have got thinner though, its tricky to do now.