I remember you mentioning the MSU in a previous discussion, Chris. For orchids and older adenium plants this sounds like a very good fertilizer. I had mentioned before my concern about the high ratio of nitrogen...it encourages quick, lush, and possibly elongated growth on young seedlings. If this is what you are striving for, then yes, this fertilizer used in a weakened solution would be very good.
As for potting media...definitely soil-less. Since around the beginning of the year I had been incorporating orchid seedling bark to bagged potting media, along with perlite and peat moss. The bark is supposed allow for aeration as well as be able to hold on to fertilizer nutrients. But I won't be adding the bark any more...my adeniums weren't performing as well as I thought they would. I think something-- some kind of chemical was added to the bark in the process. Or else it's just the bark's characteristics that eventually make the potting media "gunky" and not well aerated like in the first few weeks. So back to the drawing board for me.
Here's a video about a potting mix that I think would be ideal for adeniums, but tweaked for individual growing conditions and climate:
https://www.youtube.com/watch?...