have just given my newly plastered(dot n dabbed) kitchen/diner a mist coat of glidden magnolia water based contract matt bought from dulux centre..i have watered it down approx 30/40% as reccommended..is 1 coat sufficient to seal the new plaster ? or should i give it another coat before i sand the walls with 120grade sandpaper & do the filling in with polyfilla ? or another mist coat after sanding/filling etc before i apply the topcoats ? + i have a sanding block but is there any harm in using a palm sander on the walls which surely would be alot quicker..cheers again