Doing Sequences Efficiently

[AyGee]

Some of you may know that I do sequential art.  For the most part, it's been alright.  However, recently, these commissions I've gotten have become more elaborate, and the slowdown I'm experiencing on my computer is reaching the point that I just simply don't want to work anymore.

I typically try to put all my stages in one file, grouping layers together while leaving the background the same to switch things out easily.  However, even trying to minimize the number of layers in a sequence file like this, I end up with a solid 20-30+ layers, and it gets really unpleasant to work with, even when I hide the layers I'm not working on.  I'm looking for ways to do things more efficiently, and so far all I can think of is making separate files for each panel in a sequence (which feels a little redundant, not to mention matching colors between panels is gonna get tedious REAL quick), or reducing the dimensions of the file (I typically work with 3-4k pixels on a dimension, though 1500 should be good enough for FA submission.  I just have to decide if I ever want to print bigger than a letter size sheet of paper).

I currently use Krita for all my work, which I've heard mixed things about.  Unfortunately, I don't quite have the free time to learn how to use another program, so if a solution can be found without having to switch to something else, it would be much appreciated.

Anyone know of any other approach I could take?  I've got several commissions to finish, and I'm simply not gonna be able to work on them is things keep slowing down the way they do now.