what can you do to make a batter firmer. Does adding an extra egg work???

To make it a little firmer, extra flour can be added. Folding in whipped egg whites can also stiffen a batter, again depending upon how loose it is to begin with.

Add more flour, or use cookie/cake crumbs if flavors are appropriate.

Are you baking from scratch recipes or a mix?
For a mix use my *original* WASC recipe
http://cakecentral.com/recipe/the-original-wasc-cake-recipe

OR add 1/2 cup sour cream to your recipe.

thanks for all the info. I planned on starting with a mix, but do scratch cakes also.