Blending new satin finish in with old

[kb9wyz]

This is rather a simple thing if I'm lucky. The situation is that I recently refinished a headstock with a satin finish. (Specifically MinWax PolyCryillic, in case that makes a difference) Of course, the end result left me with a line between the new coats and the part of the neck with the original finish. So I need to get rid of that line.

The questions are:
What grain(s) of paper should I use to sand down the line?
Should this be wet and/or dry sanding?
Will I have to give the smoothed out area a final once over with the finish?

Thanks all!

[kb9wyz]

Please, someone. Research for this has yielded no positive results. All I can find is stuff on dealing with glossy finishes.