Yes, GO is great stuff, and makes a HUGE difference in the glossy print process! We even use it on glossy color prints to achieve more depth and punch for some of our studio clients. The smooth/even printed coating is always better than spraying- there are no harsh fumes, it applies a nice even finish every time (sprays can be tricky, and frequently run/glob, or get stuff stuck to the surface), and you don't have the environmental factors.
The default 30,000 GO curve works well for many gloss papers, but we have found some papers look better with two coatings of 30,000 (for example, Canson Baryta Photographique), or a single coating of more GO, so it's certainly worth experimenting to determine what gives the best results with your specific setup and media.
Best regards and happy printing~ Dana