I always base in Vellejo now. It's perfect for oils. My oils are
usually dry overnight, unless I'm using a color that has particularly
high carrier content. I try to avoid that though, and since I spread
the oils out, using as little as possible over as wide an area as
possible, the paint dries much faster.
I have been known to scrape minor errors like those you describe with
the tip of an exacto blade, but it takes a careful hand. You shouldn't
have any trouble just touching up the oils over the acrylic mistakes. I
do it all the time. Don't worry about cracking or anything like that,
unless you're glopping the paint on in thick layers, which you
shouldn't be.