I had actually been wondering the same thing for several of my costumes, just because I use mildly scented soaps/lotions on a daily basis, and it's an amusing and random thought to entertain. More likely than not, I'd completely forget what I was planning to do once I actually got in costume. I may actually use the tea trick for my 10th doctor costume... that's a really good idea.
I agree with the roses for the pink dress Ciel - possibly look into some essential oils along those lines, and dilute them with water, heavily. I've done this for a bergamot oil, because sometimes I just want to smell like Earl Gray tea - the scent stays with you, but it's really subtle. You could likely doing the same thing with a rose or gardenia oils.
Not sure on the male Ciel - you could always see about getting a little travel thing of Old Spice body wash - it does stick with you, and provide just the hint of the spicy man smell... without the bear-mace anger of Axe body spray.
Convention Line-Up: Dragon*Con 2015
1950s Celestia (MLP:FiM), Lorna Dane Serval Industries (X-Factor)
Adult Loki (Loki: Agent of Asgard), 10th Doctor (Doctor Who)