Pacifier Use

My LO is 4 months and has NEVER liked pacifiers. I've tried giving them to her several times and she always just spits them out. However today she hadn't napped (4 month sleep regression!) and she had the hiccups, so I tried giving her one while rocking her to stop the hiccups.....lo and behold and she took it and promptly fell asleep!! I was shocked. Then tonight I was feeding her to sleep like usual and she started getting fussy. Lately when this happens my husband has to rock her to sleep. Instead I thought why not try the pacifier? And sure enough, again she took it right away and fell asleep!! I feel like I just stumbled on the best thing ever! LOL Being a pacifier newbie, how and when do you use them? Just at naps or bed time? Only as a last resort? My LO is a terrible car rider so maybe in the car? All suggestions are welcome!