By higher resolution I mean a 60x48 map at 300dpi. Kind of like the maps that came with D&D back in the early nineties (and maybe still do).
I know printing at 300dpi isn't necessary. I print great photographs at 254, 221, and even 185, depending on the printer I send it to, but I'm sticking with 300dpi because it is more than enough and it makes math easier...

Here is a capture of the clouds on a 60x48 document at 300dpi
Click image for larger version. 

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Can you imagine moving all those little pieces around to create a coastline that matches your sketch? Bleck.

So is there a way to generate large difference clouds, or get the same effect through other means?
I'm currently doing what I think Azelor is suggesting, arranging continents in a 2000x2000 pixel document, scaling them up, and going around the edges with the brush tool and eraser so the coastlines don't all look like stair cases.