Tub of axle grease & a good cleaning. Super easy if cartridge bearings & the freehub slides right off.

Otherwise if freewheel &/or cup/cone you might as well pull the axle & service the cup/cones axle bearings, pawls, etc, all in one shot & be done with it for the next few years. Any shop ought to equipped to do this with minimal turn around time if you don't have the tools. And buying tools for a one time job doesn't make a lot of sense.

I say this because if the pawls are sticky, theres no telling how old dried, or congealed the grease is. Congealed grease would indicate a long time since anything back there was serviced.