I have the same micro worm culture going for a year now. I don't always need it, but faithfully make a new batch every 10 days.
Empty deli meat plastic container, with hot pin holes in top (numerous holes beat one large hole in keeping flies out).
Cheapest Instant Mash Potatoes I can find. (Oatmeal gets smellier, and flies seem to prefer them to potato)
I put an eyeballed measured cup o potatoes in, add about equal amount water FROM AQUARIUM in. Stir and "furrow" with a plastic fork. (You can make neat rows like a farmer planting corn if you like) "Pepper" with a lil Brewers Yeast. Then I use said plastic fork to plop and furrow a forkful of old culture to da middle. Cut a paper towel about an 1 1/2", dunk it in your aquarium water, and place it on da creamy center o worms. Crisscross it with a another, slightly smaller, dampened (from aquarium water) paper towel. You can now use tweezers to pluck the paper towel and wring out to feed your fish, without worrying about adding potato or oatmeal goo. (Also can use the little paper towel to "squeegee" the sides of container.)
When replacing the paper towel, it is now re-wet with new aquarium water.
The fork gets tossed. I want no confusion with it later on.
I have back up containers, and start the whole thing again in about 10 days, with fresh paper towel scraps and a new plastic fork.
I just wish something would eat fire ants. There are unwanted "cultures" of them all over the place.