http://www.microrao.com/micronotes/antibiotic.pdf

You can follow these tips on pdf but use your own drugs as long you know their concentration.

The above site is pretty good, but only deals with discs that have current antibiotics as their test system.  I will check for references, as their is  a book of methods that needs to be checked.  But in general the following will give you basic information.  Purchase blank discs, pipette various amounts of your chemicals on them so you have a variety of doses, and then test them at the same time you test standard prepared antibiotic discs against the various types of bacteria you have chosen.