Just about ready to scrim / skim the drywalls in the garden room. Just need a steer on the best mud (plaster / filler) and perhaps a bit on coverage so I don't over order or miss out on potential price breaks. Do I buy ready mixed or powdered? I will also invest in a ROTAX for sanding / finishing as I don't yet have a large (ish) orbital sander. Any and all contributions accepted.