All humans and even animals learn better from something unpleasant. (no pain, no gain.) Words alone just simply won't do. I haven't seen great behavior come out of time outs, either. I am surprised that parents will tell you this works. I've seen agressive kids remain agressive throughout the years when parents use time outs.I know two women who both have 4 year old boys who constantly bite other kids. They have been telling them for years (with an average voice) - dont bite, and then they sit them on a chair for 2 or 3 minutes. Now if time out worked, why would they still be biting two years later? Both of these families have older boys (7 and 8) that they also use time outs with and they are aggressive as well. it has not curbed thier behavior, at all.
If you got caught doing something wrong, like speeding, and you knew that every time a cop pulled you over, he was going to have you sit on the curb for two minutes and then you would get released to go back to what you were doing, would it curb your speeding? What would teach you better? Someone asking you to sit on a chair for a minute so you can rest,.. or a painful sensation? Pain is a natural consequence and it immediately tells the brain- dont do that again! ( like a burn when you touch something hot, for example) You have got to give him some kind of pain sensation along with a STERN command to stop. Even out in nature , the moma dog will give a growl and a quick bite at her pup's neck to teach him he is doing something wrong.
I used a slap on the hand and a stern command with my children when they were that age. There is now a product on the market for nail biters to keep them from putting their nails in their mouth, called "No bite." It is very unpleasant. but it is safe. It probably has capsaisin (hot pepper)oil in it. You can use it with a sharp command - NO!NO BITE! You can put a tiny drop on your finger and put it directly on his mouth/tounge the minute you see the infraction. I guarantee after two episodes he will have learned he doesn't want that sensation again, and the problem will be RESOLVED. Also the idea of using separate cribs next to eachother is a good idea, and you need to do that anyway to protect the child being bitten.