So i've just (about) finished a whole reno and did all the stopping, taping and jointing myself. The house is looking mint and it's fun doing one room but not every room ! If I was patching in an old socket or cut out, I'd backstrap the hole, cut and screw a piece of gib to fit and then skim over it - for larger holes / repairs I'd tape the joins as well. All is good with the repairs and on the odd occassion, if I sanded back a little too much and some tape appeared I'd just reskim a little more plus 4 ontop and sand the next day.

I've noticed that the new layer of plus 4 seems to sand at a different rate from the previously sanded layer - the top or last layer applied is harder and it then becomes difficult to blend edges etc for an almost invisible finish.

The only way around this is to either prime the repair ( which seems to create a new uniform surface) , reskim the dips, then it sands fine, or reskim over the whole repair, ensuring all previous plus 4 is covered, and then gently sand the 2nd topcoat back to level, ensuring the bottom coat of plus 4 isn't reached or you'll get an edge.

I do mix some water in with the plus4 (says you can add some) to increase it's workability...Could that be setting the compound differently or could it be previous dust on the surface from sanding efforts affecting the hardness.

Difficuly to describe but definitely happening. Thinking it must be me so keen to find out what I'm doing

Thanks for any advice