You can try Walk In, Walk Out or a version of Pick Up, Put Down where you just do the put down.
Use reassuring words and make sure he knows what is going on.
With my daughter when we are having bedtime issues, we do our normal bed time routine and then we tell her...."Grace, now it's time to go to sleep. Mommy is going to put you in your crib and you need to go to sleep by yourself like a big girl. I love you so much. " If she cries I rub her belly or head while she is in the crib and tell her..."Everythings OK, we are just going to go to sleep now....Mommy and Daddy are going to go now....go to sleep, etc.".
For us WI/WO does not work as she just gets more worked up and stimulated, so for my daughter she does best if we aren't in there...she usually cries for a few minutes and then goes right to sleep (on the rare days she is having issues with something). I am not advocating CIO (cry it out) at all. If your lo really needs you then you of course go in, but some lo's just need a minutes by themselves to work it out. If we are in there she will not go to sleep and if she does it takes FOREVER (1 HOUR OR SO) but if we leave she's out in about 5-15 minutes.
It all depends on your lo and what works best for all of you!
I would check out the sleep boards for more advice on how to go about things and they are the one who know best!
Melissa