1- Are you sure it's the freehub body rubbing? Some do have a "rubber" seal on their back side, being a possible friction source as well as making simple dripping oil through the body harder to do. trying to avoid the best service method is likely to cost more time in the end. Pull the axle and maybe the freehub too. Or just go to another wheel for now and return to the OEM wheel later when time is of less value.

2- Detanglers, Gryos, Orys are just one more device to hinder good cable action. This with the often poor brake set up in general mean that many of these bike have very ineffective rear brakes (and the Potts Mod ft brake cable running through the stem bolt is equally poor a choice). I suggest bypassing the Gryo. remove it and run casing straight back. The vast majority of kids riding these freestyle bikes don't make use of the design, don't do the tricks.

One aspect of the bike recyclerys that I have talked about with the two in my town is that setting the bikes up to need less attention after they get given out is a good thing. But this takes some experience and judgement. Both of these intangibles are in short supply with the usual volunteers. Andy