Question time Community!

I'm developing a world map for a good size company. They are currently using it for a 8.5" x 11" booklet. Later it will be used for a full size fold out map.

My question is what size would you work at and what DPI? I usually work at 50% for the hand drawn part and scan at 300 DPI, then do my inks in photoshop.

With that said I want to hand ink this map so what should I do the original size at? And what DPI would you scan it in at?