Soak in what?

Silicone is generally very tolerant of water, even with reasonably strong soaps. Won't need overnight, assuming you're using dishwasher or laundry soap, and neither will leave anything behind as long as you rinse well. A couple of hours is all that needs, even for really funky stuff like garlic and onions (what? I don't shove things up my ass for fun, but I used to cook a lot, and the volatile chemicals in alliums and such are going to respond similarly to the volatiles that are in rectums).

If you want a longer soak just for satisfying your mind, a baking soda paste is what you want. Just plain old arm & hammer, with enough water to make it spreadable. Slap it on, let it sit overnight. Sovereign against damn near any smell.

Fwiw, a condom will save your the hassle. And it won't change the feel of the toy much, if at all. Well, latex won't. Supposedly the other usual materials have to be thicker, and feel different as a surface. But latex condoms have a very similar texture to silicone when stretched tight the way it would be on a toy, as long as you get the right size condom. They do make smaller condoms that should fit a buttplug even, though you'll have to order them online. But any proper dildo is vaguely phallic, and a condom will fit just fine, and make cleanup much less annoying