I've been using tacky flux to solder small pin-pitch packages with a flat tip, and it's been awesome. But it is quite a terrible time when it comes to cleaning. I've tried 70% isopropyl alcohol up to 91% Isopropyl alcohol plus an anti-static bristle brush. There always seems to be a matte, sticky finish when the alcohol evaporates, and I can never seem to get the flux out from under the chips. How do you get your boards so clean?