Hi Brokin, get some 180, 220/240, 320, 360 grit sandpaper should be enough. I'd give the veneer a light sand with 320/360 grit. Rest of the body and neck sand from 180 to 360 grit. Remove all the machine marks, usually worst on the bottom/bum edge of the body.
Don't glue a bolt on neck in case you need to remove it or shim it. The bolts will hold it in place. I'd paint the body and neck separately will be easier to work with and hang to cure.

Best of luck