So I have a world map made and I want to start drawing out regional maps. My problem, however, is that I am having trouble getting the shapes and proportions accurate to the larger map. What sort of techniques have worked for anyone else who has made regional maps of their world maps? I was thinking that a grid system may be my best bet.

Note: I hand draw my maps and then do finishing touches in GIMP which I am still learning

My world map
Scan.png