- The only thing I can think of is to give them some kind of waterproof
sealing first, such as an acryllic sealant or the like. Maybe even a
really sturdy scotch guard will do. Basically, you want the paint to not
soak in, but stick to whatever sealant is on the outside. (Then of course
seal it again once painted).
You may also find more luck with enamel paint instead of spray paint. I
find that brush-on paint (esp sturdy ones like enamel) absorbs less into
the fabric, since it's less "water".. So paint specifically designed for
fabric might be another option (although I always found that to be more
expensive than a gallon of metal paint).
My lack of technical terms is disturbing! But I think you know what I
mean. Seriously though, spray paint is usually the worst, so don't get