you can use a fish emulsion for foliage feeding, just follow the directions on the bottle and to start out with, fill your spray bottle about 1/4 at first and then build to full strength. You dont want to go full strength right from the start, you can stress the plant, burn the leaf's, send your plants into lockout (personal experience - all this can be done if you spray to early). I think it would also depend on what stage of growth you are on, if your talking about clones, then you only want pure water, and if your in flowering stage i would think you dont want to spray the flowers.

You can get the fish emulsion at walmart for around $10, pretty big bottle that will last you a long time.

Hope that helps.