I usually get 74-76% efficiency with BIAB and a coarse crush from the LHBS crusher. My process looks like this:
-heat strike water
-put bag in pot and stretch over the sides
-scoop in grain and stir continuously (2 people)
-check temps and adjust
-wrap kettle in a blanket and wait an hour
-occasionally I check temps and stir once or twice during that hour
-after the mash, I stir up the grains really well this time, then I collect the bag and pick it up. I let it drain into the kettle until it slows, then I lower it back in the pot, stir, and repeat the draining process.
Usually after the draining has slowed I will put the bag into a fermenting bucket or other vessel and let it continue to drain while I heat up the boil. I let it sit for about 20-30 minutes then I pull out the bag, dispose of the grain (or recycle it for your purposes), and pour that wort into the kettle.
On my last batch with this method I got 74%.
Hope this helps!