I use a paasche air brush to apply the latest generation of water born polyurethane on all my wood pens. The #5 needle set and 40 lbs. pressure, applied on lathe at slow speed works great with uncut material. The poly surface dries too quick to get a good finish so I add 5% retarder. With retarder recoating can be done every 15 to 20 minutes. These finishes are high solid content and build quickly. I usually shoot 3 quick coats, allow to cure over night, sand and shoot 3 more coats. The largest drawback is the curing time. I allow at least 3 days curing before the final buffing, the longer the better as a harder film buffs to a higher sheen.
The colour is great, no discolouration what so ever. These new finishes do not have the bluish hue that the earlier products had. For oily woods like rosewood I seal with Super Blond Shellac before spraying the poly.