I follow BRM even if I have nothing. My BRM is that I don't buy in for anything with more than 5% of my BR. So if I were you I would only feel comfortable playing Bumble Bees until my BR dropped to 2.20. The best way to actually build your BR though isn't the bumble bees, but play more PO like everyone else is saying. That's where you will get the big boost to your BR.