Chicken wire mesh on Sherman Firefly turret.....

[David Herbert]

Since this was a field mod there would be no official way to do it and the crew would just use whatever came to hand. It would not be practical to cover much of the top of the turret because access is needed to get to the hatches, which then need space to open into. Also vision from the periscopes and space round the 2" bomb thrower must be maintained. Camoflage from above was not too critical as we had air superiority after the invasion and tanks make such clear tracks that you can't really hide them as a bush anyway.
As for method of fixing: that would have been made up by the guy doing it. If he had welding facilities then bits of bent rod welded on as hooks would work well. If not then he would be limited to using wire to tie the netting to any suitable features. It didn't have to be neat, just had to work.
Sorry, there is no definitive answer to your questions other than "it depends" !
David