The three rolls is about right. You want the wings covered without seams and then add your trim. It is very dificult to get a seam to hold without puckering something awful. The one exception to this is if the ribs are cappped. I have cut stips of covering that would span a bay including th caps. I used two colors and put down the light color on every other bay and then covered the open areas with the dark. This gives a very visible bottom color scheme. You would use this on the bottom only. On the top though you need to use monokote over the base coveing and use the widex method. Trying to iron seal it over the first covering will leave bubbles in the covering.

Keep your coveing pieces as large as you can and cover from the back forward on the fuselage so any seams open down stream. Expect a lot of scrap when covering.

There is a couple good articles on covering here on RcUniverse. I'm sure someone has the links at their finger tips. Sorry, I don't

Don