Which is the best branch for reserve/guard duty?

Easily Air National Guard. Tons of money, lots of opportunity. the difference between guard and reserve is who runs it. Reserve is strictly federal while the guard is funded by both the state and federal government. A lot of time the reserve runs out of money very quickly and you will not be able to do much more than the minimum requirement of one weekend a month, two weekends a year. Guard generally doesn't have this problem. They get a lot more training in.

Depends on what his skills are and what he wants to do. I know the Navy reserves has programs which would allow hi. To come in at a higher due to background experience. For example, electricians, machinists, plumbers, etc., could possibly come in as an E-5, or E-6 depending on their years of experience and level he achieved in the civilian world. Best bet would be to talk to a reserve recruiter, as they would have more information for him then an active duty recruiter would.

CWO3 (Join to see)
It really depends on his background. If he has extensive experience in an in-demand career field, and advanced degree in a needed field, etc., a Reserve/Guard recruiter might be able to work with him.