Dormammu said: Watch for the covers you need in vaults. They often come around in Taco vaults so you could try hoarding DDQ tokens for short periods of time until one is flush with the covers you need.
That's definitely part of the original inquiry, because I've been trying to weigh the potential risk of wasting BH covers (if they happen to generate in the one wrong color), versus the guaranteed loss of extra covers on the vine. I've done this before when I know I have a backup plan like DDQ that will save the unlucky BH covers should they occur, but I'm guessing that the frustration of wasted BH covers (should that happen) would outweigh the potential gain, so I'd probably be hesitant to try it without that kind of protection.