I too am a huge fan of Silvercreek's resin. For coating the back of copper johns, I haven't found anything better. Before I was using CCG. I would goat a layer of CCG Thin and then add a coat of the Hydro. Silvercreek has replaced both.
However, Hydro does still play one important role in my tying: parachute wing posts. Because it is so thin, I can place a small drop of it directly to the hackle which flows down into the post. Before hitting it with uv, I make sure that any of the very small trace of hydro left on the hackle is removed (a very, very small amount). Hit it with the uv and you're done. I landed over 20 cutties on a parachute adams this past summer. I will fish the same fly again next summer. I love Hydro for this!