External moisture board!

JR777

New Member
Hi All,

Averagely new to plastering, but not too bad working inside now. I've have though got some external moisture board to plaster and not sure of the approach.
It's fully covered under a deep porch and won't get any direct rain on it (although subject to moisture in the air).
Wondering what to use for joint and fill and whether I can use Multi.

Thanks for any help.
 
External moisture board!
 
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