So here's my experience over the last 8 months or so.
PVA is a pain in the arse. It's super hydroscooic, it prints in blobs and strings etc and it's very expensive.
I have found that for best results I print supports from extruder 1 and only print an interface layer of PVA from extruder 2 where support meets model. This has several advantages, it's cheaper because you use less of it, its quicker because the machine doesnt need to keep swapping nozzles, and it has less chance of causing problems.