OK, so I am using some Fuhr 260 waterborne industrial aluminum oxide modified urethane - and learned an important lesson on my practice boards...
Never use a roller to apply this stuff. It will leave little bubbles on the surface, which do pop - but they leave little craters behind... I suppose the bubbles pop after the surface begins to set up, making the self-leveling properties of the coating basically useless against this condition. I tried 1/4" nap sleeves, both synthetic and mohair - both were awful.
Brushing it on works, but even using the finest bristles, the brush marks don't quite level out enough for my tastes. I found a paint pad worked best for HAND application of this product. Also, with any hand application of this coating, it can be helpful to wave a heat gun on LOW HEAT setting over the wet surface of the coating - this will cause the bubbles to form & pop earlier in the drying sequence, thus the bubbles tend to pop before the surface tacks up too much and it self-levels MUCH better. Strange but true.
Ideally, this coating really wants to be sprayed on. I will not personally attempt any other method in the future.
Just thought I'd put this out there in case anyone has to use this stuff down the road.