Koverall is a wonderful product. Paint your framework with nitrate dope. You want to just paint the perimeter as you want it to move in the center when shrinking. Give it a couple good coats with light sanding between coats to take away hairs and bumps. Then you lay your covering on and attach it with more nitrate around the perimeter. When its dry you shrink it with an iron and you can smooth out the corners with the iron. When done according to the instructions, you will have a nice drum tight covering. You must lay it out length wise on the wing and fuselage, so order accordingly. I like to have two of the large packages on hand for a 100"+ monoplane.
The one thing nice about a painted surface is you will never have to deal with wrinkles and sags again. Try it, you will like it.