How to go from to bottle?

My son is 3 months old, and I will be trying to concieve again in Dec when my husband comes home for R&R from Afghanistan, and I need him to start taking a bottle so when the time comes for him to be weaned from milk to just foumula I can do that. Want to make sure I have no hormones left from nursing before we try again, think that was the reason we were unable to get preg before he left. I have tried all kinds of bottles, from avent to flow to soothie, playtex gerber, and the list goes on, he just will not take it, and after 30 min being alone and trying to do this, I give in. I go as far as making sure the nipple of the bottle is warm as well, does anyone have any advice or tricks?