My favorite "rattle can" flat finish is acrylic craft flat finish
paint - thinned out to about 50-50 and applied as a wash
with a brush.
I use both the semi-gloss and flat (and own but have
never used the gloss - haven't needed it).
The biggest advantage is that there isn't any overspray
to clean off of wheels, mask to protect from getting on
windows, etc. I also like the way it flows into the
hollows, cracks, and crevises rather than 'missing'
them like anything sprayed.
- Jim B.