Holster, open top, that covers the trigger guard ( BladeTech), 2-4 mags and there pouch's
A couple mags one mag holder on your belt. More if your run'n a BB and 10 rounders. No sling
Shell caddy's of some kind. enough to carry say 12 rounds. If you don't have em. A dump pouch will do. Not the fastest way, but it will keep you shooting. 7.5 or #8 birdshot
If you need some shotgun practice I will be running a shotgun only practice stage at Richmond on Nov 12. More than likely in Bay 4
Hope this helps.