If I were you, I'd go ahead and drop the money for a commercial flask medium for your first time flasking, at least. That way you don't have to think about quite as many variables in figuring out what went wrong if something doesn't go according to plan. Numberous suppliers (e.g. PhytoTechnology Laboratories) sell various media, with and without charcoal and banana, some of which are not specific for mother or replate flasks. Just be sure to note the difference between the 10L and the 10 x 1L: the former is in one large package, and needs to be weighed out with a very accurate digital scale, whereas the latter is prepackaged in smaller amounts, and needs only be dumped into a liter of water and cooked.
So how are you sterilizing your flasks, and what are you using for flasks? For that matter, how are you creating a sterile working environment? Glove box? Flow hood?