First, call around and see if any photogs have some unused backgrounds, the
average studio shooter will go through a background for awhile and then it
will fall out of favor, either cause they are sick of seeing it again, or
maybe cause they didn't like it in the first place.

Frankly painting your own is a PITA, the market is rather competitive so the
markups are not that much, you will find that you would probably spend as
much on the materials and paint as you would buying one (though you could
make several, and some local pro associations will have background making
parties which is even more fun cause then you have experience people helping
out.)

Ideally you want at least 8 feet wide, six feet minimum.  The simplest way
to paint is to coat it flat gray blue, then take some warm tone, gold/tan
and water it down, take a long haired brush, same kind you'd use to paint a
house the old fashioned way, and a stick or pipe, holding the pipe up, whack
the brush against it so the little bits of paint splatter about where you
want it, work from near the center out, not too much, this effect is subtle,
but is as effective as having an artist paint vague clouds.
Cost about $200, would sell for about $400, takes about a day, use household
latex flat.

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