Can I use this for paint prep before primer?

Yes. The grinder handles surface rust, old paint removal, and edge blending on metal. Work with appropriate grit attachments and wear eye protection — metal dust flies fast.

How long does the 3.7V battery last per charge?

Battery runtime depends on load and attachment. Light polishing runs longer than heavy grinding. Charge time is quick enough that most users keep two batteries rotating on smaller jobs.

What attachments or accessories does this come with?

Unit ships as a bare grinder. You'll need to source grinding wheels, polishing pads, or wire wheels separately based on your specific job — this gives you flexibility to match the right attachment to the task.