click on guitars above and navigate your way to the tech section. THere is a tutorial on neck sanding, but it is directed towards necks whick just have a
clear coat on them...but the same principles apply to a fully painted neck as well.
You don't have to put anything on your freshly sanded neck, most folks here prefer raw wood...It is very nice.
I am nearly finished with stripping a neck similar to your situation. It was painted and cleared with very thick stuff. It has taken a lot of work to get it off. My recommendation is to use a power sander to break through the clear. Once into the body of the paint, switch to hand sanding using some creative shaped sanding blocks. My favorite was a miniature baseball bat shaped pen that I wrapped in sand paper to handle the subtle contours on the neck.
I started with 100 grit and worked my way up to 220, using that grit to get the last of the paint off. Next is the polishing phase, 400 and 600 grit to get it baby smooth.
I did find something strange though. I think my neck was built, then sealed, then painted and then clearcoated. I have all the paint off but there is still a layer of dull looking finish stuff. So I have a little more work to do yet.