HELP with bodywork

So if you do use spot potty im assuming you should probably go over it with high build afterwards so its not just openly exposed, even when dry? And another quickie guys, when blocking the high build, if i find low spots that need to be built up with bondo, do i need to bring those spots right down to bare metal, or can i apply filler over the high build primer?

Thanks so much guys for everything really, this thread has been a great help...hopefully when my car is painted in a couple of weeks i will have some pics up for you guys

thanks a bunch
Matthew