I have been a professional house painter for many years and finally shut
down my painting business last august to pursue designing gardening web site
and producing garden videos full time. My personal prefrence would be to
use a solid color stain to paint a fence. This only requires two coats, and
will normally outlast paint since it penetrates the wood, where paint is
only covers the surface and will peel.

If you have a dark stain on a storage building, then you need to use a
primer/stain hider. If the current stain is oil based then I would prime
with Zinnser BIN (tinted toward the color of the top coat), if the current
stain is latex then I would use the Zinnser 1-2-3. Sometimes these dark
stains do require 2 coats to cover them enough so that when you appley two
top coats you get the color you want without the bleedthrough..Then I would
paint the buidling with Sherwin-Williams Supepaint latex. Paint the siding
with a satin finish and the trim with a gloss or semi-gloss.

A lot of these storage buildings have T111 siding that will suck up paint in
a big way. You will definately save a bunch of money by priming first since
primer is much less expensive than quality top finish paint. The primer will
seal the wood so that the paint goes on easier and not require as much.

Bobby Baxter
Happy Moose Garden
http://happymoosegardens.com