Hi;
If you cannot get " DOPE " there is a way to do it .Take " Spar " brand MARINE Varnish or Shellac , Thinned by fifty percent and you should be good to go . When it's dry you can apply the color of choice . T.B.
P.S. A secondary thought . When you build the kit they tell you , or used to , Wet with a spritz of water , when dry the covering will be tighter . Don't do this if you are going to put regular paint on it ! It will shrink so much it will split !
Take craft clear in the spray rattle can , and apply a thin but thorough coat , Let dry and then paint to your heart's delight !