My suggestion would be to use Illustrator if you have it. If you don't I would suggest selecting what you want to resize, then using Edit: Transform: Scale.
I would recommend doing your whole strip/page in mspaint, saving it, and then doing special effects, lettering, or whatever in photoshop. doing sprites in paint is quick and pretty easy, but you can't do much with the simple tools in paint as far as making it look super awesome. so try doing just the panels and such in paint; after all photoshop was invented to doll-up photographs, not making sprite comics....
~*~
#253 in Comic Book/Story #344 Overall ~*~ #383 in Comic Book/Story #517 Overall
I would do it on paint, and keep it PROPORTIONATE when you're resizing. Because a sprite is pretty much colored squares, so they have to stay that shape. I think you have to hold shift while dragging a corner.
Always resize sprites in increments like 25% or 50%.
Keep your sprites indexed and it shouldn't blur. I'm not sure if that's correct, though; I used to only resize them in Paint Shop Pro, which had an option that would definitely never blur sprites.
Yeah, uncheck 'anti-alias' when you select the area to be resized and mess around with the drop-downs in the resize window untill you get the result you want.