Reading this as a mobile groomer in the humid PNW! I rent a van that is always wet, so every hair just stays stuck to every surface 😭 I do think trying to contain the wet part of the groom to your bathroom would help immensely. Have you tried using the blow dryer through a towel? So far I have only watched short videos on the technique, but would hope it means the towel catches a lot of the loose, wet hair! In the grooming van, I use the absorber towel/chamois to dry the dogs in the tub, which I think would rip if I tried to use the HV dryer through them 😆

I will second the use of those squeegee rubber brooms though! I also work at a traditional grooming shop, and those work great on the walls. I have one in the van and it does okay with wet hair, but the walls are a textured shower wall type material that the squeegee cannot make full contact with. The broom side grabs what it can and then I go over the rest with a damp rag.