As part of the Oncidium alliance it should do quite well in s/h. My Oncs love it, but as you mentioned Rst is a cooler temp sub group The evaporation around the clay pellets will cool the roots somewhat depending upon your ambient conditions but if your growing area is on the hot side, it may not work. Maybe someone who has Rst in their collection could be of more help.
As for MSU fertilizer, you could contact Firstrays
and see if they ship internationally. Good luck!
Here is a link:
Nutrients