Hi,

I have skinned some car parts for my car using the XCR kit.

I have skinned quite alot of parts and have got to the final stage of finishing with 400-1200 grit sandpaper.

I am looking to speed up the process by using a sanding machine with the 400-1200 grit papers.

Which is a good sander to use?

Any sander, it doesn't really matter. Air is better than electric for this sort of work, but you need a fairly capable compressor. Electric can work too if need be.