There are sure a few ways to skin a cat that is for sure........ Going back to the original post of the Estes instructions now reading.... prime the model, sand, prime again and repeat til smooth. I have tried this technique and it does work but you do use a lot of primer paint and added weight, not to mention all the sanding. The old Estes and Centuri instructions have you brush on 3 to 4 coats of sanding sealer or filler sanding between each coat then paint. This is how most of us did it back in the day and how I still do it. Even as a kid this technique would give me a pretty nice looking rocket. I really enjoy the look of a built rocket before painting, with the bare balsa and cardboard, balsa parts so papering is out of the question for me. My last couple of builds I have been using Sand N Seal by Deluxe materials and it works pretty good. Aerogloss sealer has always been my sealer of choice but it is no longer being made......Dang tree huggers. I have tried Fill N Finish but too much sanding and a big mess for me to use. The Sand N Seal is pretty cool because now I seal my balsa at work since it does not produce an odor.