Dear BP addictive,
Double anal penetration is definitely not the most mundane thing we discuss, but there have been some insights on this forum previously. We all do know that double anal is possible and very pleasurable, but it does require an additional warm-up.

With anything anal, it's quite simple - anything goes, while you do proper preparations - aka a couple of orgasms prior to the act, A LOT of stretching and working up the sphincter with progressively larger tools - and add enough lube. By "enough lube" I mean you'd wanna go bonkers with how much lube you use. Don't care about the mess - your safety and comfort should come first.

Since the bum has zero natural lubrication, you should take as much as the bottle can hold. If you prepare and use lube (no numbing ones, please) everything should go down flawlessly.

Good luck