Infiltrator + Toxic is great for putting Substitute Stallers on a Timer, but if they have a Status curing move, you'll need offensive power to keep the pressure on. Specially, Crobat gets Sludge Bomb, Air Slash, Heat Wave*, Dark Pulse*, and Giga Drain*, but it all comes off a lackluster 70 base stat. On the Physical end, the movepool is less diverse, but a better 90 base stat can make use of Cross Poison, Brave Bird, Zen Headbutt, and Super Fang*, its most viable options, plus U-Turn. Crobat also carries excellent support, though, with Tailwind*, Haze, Confuse Ray, Mean Look, Defog, and Whirlwind. So there's a lot of ways to go.
Mean Look, Toxic, Roost, [attack] on the Infiltrator set is good for trapping and taking down defensive Stallers ; but for a more offensive set, I wouldn't recommend Mixed, so pick a Physical or Special set of attacks and go for it. The Special stat is lackluster, but the expanded movepool is very attractive, as is Crobat's access to Nasty Plot (Egg Move from Honchcrow) so take that into consideration.
