In my plant nutrition research lately, I found something of the basis for the "orchids cannot use urea directly" stuff. It is true...and false.

All plants have two absorption paths - roots and foliar. Foliar absorption is through areas of cells that are closely associated with stomata referred-to as "plasmodesmata". As orchids have evolved mechanisms to conserve water - fewer stomata, most stomata on the under-sides of leaves, thick (waxy) cuticles to prevent loss - foliar nutrient absorption is generally much less of a factor than with terrestrial plants, but it still varies with the plant.

The plasmodesmata tends to allow the transfer of nutrients into the leaves that are non-polar (like urea), but tends to not pass polar ionic species like nitrates and ammonium compounds.

Velamen on the roots, as I said before, has sites that specifically capture ions for absorption. By contrast, it is very poor at capturing less-polar chemicals like urea.

So the upshot is that orchids CAN use urea directly, but the absorption path is primarily foliar, although that tends to be limited in its absorptive capability. The urea has a much more difficult time of entering through the root system, so it must decompose before it can be used to an appreciable degree that way.

I used the MG orchid food when I started and it didn't seem to do anything to help them. Sure the couple plants I have didn't die, but also didn't do much more then grow a little. I switched to Better gro bloom booster. Yes people say not to use it, but it was the same price as the non bloom booster and the non didn't have even enough numbers for me. For me personally I have found that having a higher N number (the first number) causes wonderful leaf growth but not so much flowers. This is VERY true to my outside plants as well. I get wonderful growth on say my hydrangeas, but less flowers. So I stick with closer to even numbers when it comes to the N. All my plants, and I mean all have had SUPER growth using this fert mixed with seaweed and every other time I will also mix in a tiny tiny splash of vodka (look up that thread).

As others have mentioned I have always done weakly weekly, seeing as though nature seems to have the same basic nutrients all the time, it doesn't just dump a pile of nutrients once a month. If my fert says 1 teaspoon per gallon, then I use 1/4 or so, but mostly it's more like 1/3 since I dump it in and let it drain out, so it's not really getting the full amount.