old paint can be a nightmare u need to rinse and rinse then rinse some more however some may not come good.sash frames not a problem if you work in a methodical manner and dont squirt water under bottom of top window.any open windows during hot weather (ha ha ha) can be closed with brush head normally ... if they cant then they dont get done ... simples.
Those ones made from brick are best to avoid. I generally stick to the glass ones.