Dress-up for me usually just involves getting into something sexy long enough to get thoroughly turned on (and have the desired effect on ratbastid or D) and then getting right back out of it
For instance, a corset, a slutty little miniskirt, a couple of strategically-tied scarves, or my Princess Leia slave bikini. It's a way to act out a fantasy, either of mine or of theirs. If dressing up or role playing doesn't feel sexy for your SO, though, then maybe it's not the kink for him/her. What is the objection they've voiced?