anyone have bondo tips?

nah, the best mixing board is carboard. cheap and just throw away when done. get a huge box and cut it up into like 14x14 inch pieces, and mix on one side, then when you ready to mix more, just flip it over. when done, discard.

also, do not mix alot more than you need. if you put too much hardener in it, you will not have time to work with it. if not enough hardener, then it take forever to dry
your first few mixes maybe all over the place as to how fast it dries, but you will figure it out in no time! fyi, once you mix it, you will be able to tell by color if it is going to harden too soon or too slow. and once you notice the color that is just right, you will have fun

the darker red it is, the quicker it will harden. (or whatever color your hardener is)