Size 2 and size 4 of this brush, all the time. =D
http://www.dickblick.com/products/robert-simmons-sienna-short-handle-filbert-series-67/
Except for the clearcoat, which I just put on with something cheap, because it’s a PITA to clean off…so they get ruined a lot faster.
I also use this to clean them :
http://www.dickblick.com/products/masters-brush-cleaner-and-preserver/
Edit, to clarify – I doubt those brushes I use would hold up half as well if I didn’t use that cleaner/preserver on them. You can use it both as a cleaner and as a conditioner (by letting it dry on them, then rinsing it off, before using them again). Otherwise, they’ll get pretty roughed up after one PYO. e.e Not unusable, but not as nice as new. And I’m not one for ‘scrubbing’ when I paint…
There’s something in one of the stickies about brushes too, I think?