The only thing is that if you don’t know your buddy’s tracks as much as he does, that might cause trouble.
You’re lucky, you’re playing on laptops so you can see eachother waveform, so that may be some good help.
Also, think that DJing is kind of an interpretation of existing tracks, and because you have 2 minds doing the thing, they can conflict
i.e. one guy would like to cut bass on this track his mate’s track to introduce, and the 2nd guy doesn’t feel to turn up the bass at the exact same time, result = no kickdrum/bass, absolute mess.
I’ve played several mixes with a friend (from 30 mins to 3h straight) on Mixlr, not at a gig.
We were able to communicate on how we are going to transition, i could ask him to high pass filter, he could ask me to add some midrange freqs etc..
It depends on the gig but sometimes I doubt you can communicate that easy, because of the noisy environnement.
A trick that you can use is to route the output of one of the DJs to the other DJ’s mixer. It’s one-sided, but if necessary, the DJ who has the “main mixer” can have a bit of control over his mate’s track (cutting, lowering eq). But note that if DJ A controls the “main mixer”, and DJ B cut the bass on his track, DJ won’t be able to restore the bass with the mixer, so it’s kinda weird but it can work wonders if mastered. Not to mention that DJ A can FX DJ B’s buildup that is also FXed, ahaha it can be crazy.
The only “real” solution I see in that case is to have played with your mate long enough, for months or even years, so that you don’t need words to communicate. It takes a long time to achieve, trust me. (OT : I was playing competitive counter strike years ago, and with a teammate, we played almost everynight of the week together for I’d say a year before we get the automatisms, but then it was super effective, knowing by experience and instinct what your mate is going to do in the next seconds)
PS : another solution i just thought of would be not to mix toghether, but one after the other, on the same setup. A “back to back”.