Here is a really slick idea for all types of model builders- a sanding stick with four different grits on one stick. From CRM Hobbies in Missouri comes a set of four sanding sticks with a stick having 600, 320, 240 and 150 grit on every stick. No digging around looking for a new stick as you polish up a seam, just flip it to the right one you need. As an added bonus, they are water proof. You can take them under a running sink while sanding or dip them in water and the grit stays in place. They are cushioned so they can go around corners too.
I was recently built the X-Plus Ultraman kit and used these to eliminate seams and polish and they worked great. I also used them in running water and also, no loss of grit and it polished up the seams well. They cleaned right up with water and a toothbrush like new.
And as an added bonus, shipping free for US customers.