Painting over uneven surfacees on cardboard and tape?

Question:

Painting over uneven surfacees on cardboard and tape?

I'm doing a school project using cardboard and packaging and masking tape. I'm painting it with the paint you use for your walls bought at Home Depot. After I paint, I can see the wavy ridges on the cardboard, they are very obvious, and I can also see the outlines of the tape. How can I paint so there's a smooth surface?

Best Answer - Chosen by Asker: You can make a primer. Ad flower to your paint til it stops dripping. This will cover all bumps and does not cost you anything... well ...maybe 2 cents.

The other option is 'waterproofing' the cardboard before you use the wall paint. Use gesso lightly to make a first layer without soaking the cardboard. That way your cardboard will retain its original shape better.