He used to do blogs, and those are the ones that have a good amount of views (30K all the way up to about 200K). All his lives pretty much top out at 2K views.
I think a Math interview would help, but Math isn't big enough to make a major impact. He might get some extra views for that particular interview, but I doubt people would stick around. He'd have a better chance of gaining subscribers by trying to get on Math's show and just be one of the dudes sitting in the chair in the barbershop, and have Math promote his channel.
It's almost like a rap song. Sure, having Wayne on your mixtape song will help you somewhat, but Wayne putting you on his album will help you far more than Wayne being on your album.