I stopped using royal a long time ago and not only glaze my cookies as a base, but also use snack-size baggies filled with all my colors to do any detail work. Its true you will not get the crisp look of RI, and you certainly couldn't do any drop flowers out of it, but the glaze is so much easier to work with AND you don't need to whip out the kitchenaide for it each time! LOL
I keep a big batch mixed up in my fridge all the time, and then pull out small amounts as needed. I've even used it for some simple piping on some of me cakes.
If you add slightly more corn syrup than milk, you will get a beautiful shine AND it does harden slightly faster. But be careful, much like RI it will 'seem' dry enough, but its like that 3rd coat of nail polish... gotta be patient for all the layers to dry. If you try and fill in with a large amount of isolated glaze - like an eyeball, you could wake up to find airbubbles have popped and left a crater. Happens periodically, so its better to do lots of thin layers than one big blob for those types of areas.
Hope this helps! I make a TON of cookies and am staring at an order of 250 Valentine hearts right now! Mixed up eight batches of glaze last night so as soon as I get settled in today, I'm ready to rock and roll with the fun stuff!