Urea is high in Nitrogen but not readily available to the orchid and therefore is mainly useless. As the concentrations increase, it can burn your roots. Not something to look forward to. Avoid it.
I use a weak dose of the same Better-Gro fertilizer. Weekly. I also use K-L-N once per month and have really been impressed with it. The only thing somewhat inconvenient is that you can't put the compound on anything you plan on eating and you can't use anything that's come in contact with it again for eating or drinking. I suppose you may grow roots!
It works though. I use it once a month.
I also use SuperThrive....Once a month. I alternate with Kelp. I find that this combination works quite nicely here in Florida. Once every two or three months I toss in some Epsom Salts....a wee tiny bit.
I'm currently in the process of trying Lime on my Paphs.
Good Luck!