Use an incline bench, set at about 45 to 60 degree incline, and lay chest down on it. Then use an EZ curl or DBs with your arms hanging straight down. It is somewhat similar to doing curls on the straight side of a preacher bench, or spider bench curls. Your shoulders are in a forward position.
You have to check so see if the support that props the incline bench up will interfere with the movement of the bar. I just squatted down a little to grab the bar and then you can rest your knees on the seat. Great pump and go lighter at first.
Something else really cool I got from Nick Nilsson was to do standing ez bar curls, but bring the bar over to a cable weight stack. put the pulley on the bottom. Wrap a towel around the middle of the EZ bar, and then take the bitter end of the cable with the carabeener and wrap it around the bar with the towel on it and clip it to itself, that will keep it from sliding around as much. Then curl with about 60-70% of the weight you would normally curl and add some weight from the weight stack. It keeps you from cheating and creates a nice line of pull so your biceps are under tension at the top of the movement.