You can load a strip with loadanimimage, and specify the sizes of the cells. Lining everything up perfectly in your paint program can indeed be a challenge, but not a whole lot you can do about that.
You can make it a little easier by using a (temporary) grid in the background, or other location markers that can help you allign the images in the animation strip, but it's still handwork.
You can make it a little easier by using a (temporary) grid in the background, or other location markers that can help you allign the images in the animation strip, but it's still handwork.