what do you mean? usually people cover the GS in silicone and then press coco coir into it to hide the greatstuff.
for planting, you would use a film bottle (with holes cut) or something imbedded into the GS and then put your plants in those. this lets you control the amount of water and gives drainage. most people just pop a bromeliad into the cups and take it out to water it. I would not fill those holes with just soil as the GS will degrade over time if it is constantly exposed to water. i suppose you could seal those holes with silicone and put plants in it as well though. it's just easier to use film bottles rather than try to fill up the holes with silicone.