If it's vertical or undercut, you need to tie it on with wire. Working by myself, I had a stretch where I wired the burlap on dry, then painted the cement on later with a cheap paint brush. If you have a lot of surface relief detail, you will have to put wires every couple of inches. It worked OK, but it took forever[\b], and I had to paint the cement on from both sides. Luckily, both sides were reachable.
If it's really steep, but not quite vertical, and no undercuts, you can soak the cement first, as normal, then use your fingers to cram the burlap through the holes in the netting. This works best if the pieces of burlap are on the small side, about 6 inches square. You'll have so much crammed into the burlap that it will take several times as much burlap as any other method, but it's way faster than wiring. Wear rubber gloves for this, the cement is very hard on your skin. Of course, you should be wearing rubber gloves anyway.