Any sanding headers tips?

I am sanding my new Headman headers and repainting them because the paint was terrible! Man, what a job this is! I feel like I am making love to them!

Does anyone have any tips to make this an easier? I'm doing this by hand and it seems to take forever!

Also, when they are sanded do you have to get every bit of old paint off? There seems to be pits and things in the header that dont seem to want to come off.

Before I repaint these, what to I use to clean them off?

Thanks!