putting him down for bed

so my 19 month old still needs rocked to sleep every night and nap. I've tried just laying him down and walking out, figuring he'd cry himself out. what he does instead is sit in his crib and talk to himself and kick the wall for hours. then i go in an have to rock him to sleep anyway. this was not an issue except I'm due with baby 2 in july. i can't tend to a newborn if i have to rock a 2 year old to sleep.

does anyone have any advice on getting him to sleep on his own?