Baby Shampoo is probably okay, as it is a pretty mild detergent. Actual BC cleaner contains a pH neutral detergent, an anti-microbial (usually Nonoxynol-9) and a silicone additive. Detergents can dry out the watertight bladder that holds the air in your BC and cause them to crack (over time). The silicone helps prevent the dry-out.First, I dump all the salt water out. Then I put in a bit of baby shampoo, fresh water, shake and dump that several times. Then rinse the outside. Store it upside down and keep dumping the little remaining water out for days after the dive. I've had my used BC 3+ years now and no problems. You can also buy the BC cleaner fluid instead of baby shampoo, but it costs more, it's hard to find shops that sell it, and folks say the baby shampoo is just as good.
Fun Fact: Nonoxynol-9 is also a common spermacide.