spray painting: if done right, if the right tip, if an experienced sprayer, and if prep done right, I feel that spray will give you a better coating and definately a pretter, even finish.
You are really getting more paint on the surface.
But, the bottom line again is, the quality of paint. This is what will tell the overall results. use paint from a paint dealer only, not a home center.
Plumbing: freeing that stuck valve can be easy and can be a disaster. I would first shut off the water in case the worse happens. Get two cresent wrenches, one to hold the actual pipe and one to assist in turning the valve. spray with wd 40, and ever so gently work the valve one way then the next. If you over muscle it, the pipe will break and its plumber time.
Once the valve is open, then shoot more wd 40 and work it in. Then never let this valve go without turning some for this long of a period. A stuck valve during an emergence is actually no valve at all. Going to the street to turn off the water will allow the damage to already take hold inside the home.