These are all great suggestions. The issue I had with waiting was that if I placed the feed trough the wrong way against a wall, the brahmin would glitch and get stuck inside the wall whilst eating when I arrived at my settlement, and then won't ever finish eating as it can't move. But I will try the other things in order to rectify that.

I always thought it was really weird that the mysterious serum removed 36000 rads, because it doesn't specify that it will do it over the course of an hour. Will definitely be using this!

Do Rad-X effects stack? Or do you mean one after the other?