Well as for the bit of tummy hanging over - I have more than a bit lol
anyway the best thing is to wear knicker/panties under that bit of tummy so they tuck up and stop the skin from rubbing, instead of wearing your knickers over the tummy.
Make sure you change them everyday as they will absorb any sweat from under there and help keep the wound area drier.

Whenever you can you need to let air get to the area - like if you are watching telly lower your trousers and hold your bit of belly up so that the air can circulate.

I personally have found blowdrying to be the absolute worst. I put a strip of absorbent kitchen paper under neath - works a dream.
Also baby talc.

So in short keep the area
1) dry and 2) protect the two layers of skin from each other.