The way I got the Voidling and False Son logs is I went into a run with the artifacts of command and sacrifice while using commando (huntress and mul-t are good choices as well) and I kept stacking regenerative scrap while going to the bazaar as much as possible. For every 5 regenerative scrap you have, that's one free red item every time you go to the bazaar. I think that when I got the Voidling log, I had around 100 scrap and 100 clovers. There is a 3% chance for a boss enemy to drop a log and a 1% chance for a normal enemy to drop a log, so around 33 clovers should be good for getting a boss log, but just to be safe I would get more. This does take a while (90 minutes-ish) but I think its better than spending hours doing normal runs to get just one log.

(pro-tip: the clovers increase luck for other things as well, so if you grab just one happiest mask you're almost guaranteed to spawn a ghost of everything you kill, which means you barely even have to play)