I've played a bit of 'normal' Deadlock before and I have to say that the new Brawl mode is even more chaotic than the regular mode. So I guess your best bet is just to hop into the game and play a couple of rounds, watch a random video on YT and then just jump into brawl, if that's your jam. Probably best to learn just by playing.
There's also some playground ingame where you can just toy around with different heroes and try them out.
Anyone here using this and Pairdrop? I've been using PD for a while now and I'm wondering if I'm missing something by not using this (as well)? :)