I don't play ctth often.. but i played a few the other day and got a 108 on edgewood tahoe. Not fabulous I know but good for me.
On an approach bunker shot i tend to use full backspin.. and give it an extra 5-15 yards on the meter... depending on the lie and elemental conditions. If it's 30-40% then even a good 25 yrds might be in order.
I think the bunker hole on the pinehurst challenge is much more difficult. You have to give that one about 30+ yds just to hit the green.