NOOOOOOOOOOOOOO
DO NOT USE A SPRAY PAINT PRIMER.
You will be kicking yourself for that if you do. It will shrink and distort the the tissue and make it very weak and brittle.
At the least, use a white acylic craft style paint. I buy mine at the local dollar/discount store cheap.
However, if you already have the dope, thin it to a 50-50 ratio and use that to seal it. Works very well, kinda stinks while you are doing it, but it works.
Even for the covering process, I always thin my dope out to 50-50, there is no need to use it full strength.
Or like others have mentioned use a white glue thinned out to 50-50 as well.