The easiest way I found is to work at 3x the publishing size so my long canvas is at 2400x50000.
Then when all art is done with CSP you can export as jpeg and resize it AS you save cause of the export settings.
Then it saves as an 800x_____howevermanypix____ and then I run the file through the online croppy tool and it cuts it up into smaller jpeg a for me.
Generally : Work at a higher resolution but not too big. Then export final art and resize that. But yeah you don't need to work at 10x the publishing size. 3x or 4x will do.
Ps: for my main comic I also do pages cause I want to make a print book. I work at a US scale comic book template at 600 dpi. Then when all art is done I make a new layer of all flattened art and copy paste the art and dialogue layers to resize on a long canvas for publishing. Cause the art isn't too big, it resized without blurring.
The blurring here is more a tech limitation than anything else. Gotta make it easy for the computer to process files so they look right.