Ah yeah, roachmilk. A year into working at the bug farm, a coworker told me about it, and we all thought he was bullshitting until we looked it up.
You need to kill the roach to extract the milk; it would be really hard to reconfigure the organ such that you could pump it out. More importantly, you get maybe a few microliters of milk per roach, after a process that is neither simple nor energy-economical. It’s only ever going to be a wealth-flaunting food item.
Instead of wasting most of the roach, you might as well eat it. Or better yet, eat your beans instead.
2 days ago I talked to a guy who said he just uses smooth plastic bottles for those roach traps, with some water inside and maybe something that smells like food.
A lot of online how-tos recommend the drop of dish soap. I personally never got it to work, I think it blocked the smell of the vinegar and flies didn’t even come close. When I tried the vinegar on its own, they flew right in and drowned in it.