I've often worked on at least 2 comics at once (right now, I work on 2 side by side with 2 visual novels and an audio project, glkdfhg it's a lot) BUT I do art full time so I don't think I'm always a great example of getting multiple projects done. I get my projects done, I just also have a shit ton of time for them compared to others.
But, what works for me is setting aside days each week for different projects. So, monday is break, tuesday is commissions, wends is comic 1 pages, thurs is game stuff, friday is a break, saturday is comic 2, and sunday is game stuff again. Kinda like that.
Or you could go bi-weekly or monthly etc etc, it's just about splitting up your time. I recommend setting goals for yourself each day or week and keeping a planner or scheduale since it's a lot to keep track of in your head. Good luck!