Making Good Soil Pipe Through Wall

[Onoff]

To get the collar in the fittings in necessitated some "enlarging" with the chisel leaving a ragged hole.

 

In the past I've just gone mad with the expanding foam, cut it flush and painted it later. 

 

BUT, obsessed as I am now about draughts, what's best? Foam first then cement via the mortar gun and a bit of clear silicon to finish off?