So i see the charts for how much batter I should use for each pan size but how do I know how to make that much batter? Do i use the WASC recipe and double, triple and just use what I need to? HELP!

Different WASC recipes will yield different amounts of batter depending on what is being added.  I find that most WASC recipes that I use yield between 14-16 cups of batter.  That would be using 2 boxes of cake mix, 2 cups flour and so on.  I always make a note on each recipe, after making it the first time, how many cups of batter it makes.  HTH