i've experimented a lot with the recipe and prep. this consistently performs well for me, and is scaled to the sizes available in my local grocery store. none of it is rocket science. you can tweak amounts without hurting a thing.
UNCLE MACK'S MAGGOT FARM (TM) (i know i'm just amusing myself. you kids area probably all to young to remember UNCLE MILTON) maggot chow:
4 boxes potato flakes (52 cups total)
1 bag confectioners sugar (7.5 cups)
8 cups BREWERS yeast
1 'tube' of plain oatmeal (2 lbs) ( i use one minute oats, but whatever)
3/4 cup methyl paraben (you might use less, or even leave it out, if you live somewhere mold is not a normal issue. new orleans and austin had MOLD!)
also a packet of BAKERS yeast and a pinch of regular sugar.
combine all ingredients EXCEPT bakers yeast and regular sugar, then store to use as needed. i use a flour sifter for the MP to make sure it is well distributed in the mix.
i have less problems with contaminated cultures when i boil the water i use. i also proof the bakers yeast.
add 1-2 inches of dry media to bottom of culture container while water starts to boil.
i also take a stack of index cards, and make 2 "accordion style" folds to each index card as the water gets ready.
as soon as the water has boiled, use some to proof some bakers yeast (after a moment's cooling). add normal sugar to the yeast mix and set it aside to do it's thing while you fix the cultures.
i pour the very hot water onto the dry mix in the culture containers as i stir it. add enough hot water to get a soupy consistency for about two seconds as you stir. it will immediately start to thicken into a paste which has the consistency of mashed potatoes. think dry-ish mashed potatoes, not wet.
i wait to put the lids on the culture cups until most of the condensation from the walls of the culture cups has evaporated. this is the time you risk corrupted cultures, so try to work in a clean area, and make sure there are no gnats, wild flies, etc. if you put vented lids on immediately, they tend to get damp and not breathe as well over time.
as the cultures are drying and cooling, i stick the folded up index cards into the media. these work sooooo much better than excelsior or coffee filters or toilet paper rolls or whatever! greatly reduces risk of mold as cultures age.
the note cards give the flies a place to climb up out of the media, and the maggots a place to pupate. i use 2 or 3 cards per culture.
now smoke one cigarette. or whatever you do to kill 5-10 minutes...
by now the yeast should be proofed, and the cultures cool enough to add the yeast slurry. just drizzle a few drops onto each new culture. i use the leftover yeast slurry (in glass jar) as a ff trap to catch escapees. i just set it next to my cultures, then throw it away as i replenish the cultures the next time.
by this time, the culture cups should be dry enough to put on the lids. i wait 24 hours before adding flies to be sure the CO2 from the yeast has had time to dissipate enough.
i think that's it. if i was unclear on any steps, let me know.
on a side note, almost no potato flake based recipes use oatmeal. it does add nutrients to the mix, and more importantly helps wick moisture so that your cultures do not dry out too fast, nor turn to soup as they age.
i also use way more yeast than most recipes call for. it is more nutritious, but more importantly leads to healthier cultures, and you can use this media for Hydei as well as all the easier flies. GET TURKISH GLIDERS. they are a bit more robust, so you have to get the hang of working with them without them 'gliding' away or crawling off. they cannot fly, but can glide for really short distances. anyway, they out produce every other fly type by 4 to 1, quickly and without fail.
good luck with your new MAGGOT FARM (TM).