how much dry fertilizer?

how much dry fertilizer should i be adding to my mix? ive been using epsoma plant tone i think 3-5-7 is the npk value. my mix consists of MG garden soil, sand, perlite, vermiculite, and about 5% used coffee grounds. ive been adding 1 tbsp. of epsom salts and 1 tbsp. of the dry fert for every 16oz (dixie cup) of soil. seems like it would be plenty but im still having to use liquid ferts as well, early on. i usually add the fert to the soil right before planting. should i be mixing earlier and letting it cook?

i would let it cook. thats a lot of raw materials. espoma is great stuff. moderation is your best bet. you can always topdress later.

thanks danny