Spray some Triflow or equivalent into the gap between the bearing race and the freehub shell and spin it around. Flip it over and let it drain. Repeat a few times, then see if that helps. If you can hear a grinding instead of the pawls just clicking into place, the freehub might be toast.

Don't worry about greasing the inside of the freehub. I recommend you not do it at all. You could practically run it dry, in fact. The only time the freehub turns is when it has no load on it, so it's not like the hub bearings. A light machine oil is all it needs. Same for all freewheels, by the way.

This only applies to pawl-type mechanisms. Some freehubs use different mechanisms, like drive rings or plates. Some share the space with the hub bearings, and in those cases the above does not apply. Follow manufacturers' specs for those types of freehubs.