hair will shrink when it locks. I think the general rule is that you'll lose at least half the length of your hair...the curlier the hair, the more length you lose. my hair was probably around 2.5-3 feet long when i started...and is now a little over a foot.
your hair shouldn't be slimy or oily after doing the BS/ACV rinse. my guess is you might not have rinsed it all out. it could also be your natural oils, depending on how long it's been since your last wash.
in the beginning, it's important to wash your hair often so that the natural oil from your head doesn't help your locs slip out. However, it's good to wait a couple weeks before your first wash to allow knots to form.
my advice would be...if you've just started (whether T&R or backcombing or nothing) don't wash your hair for two weeks so the initial knots can form. after two weeks, wash as often as possible (maybe 3-4 times a week...every day, if you want) but be gentle. try squeezing soap into your dreads (like a sponge) rather than rustling your hair all about your head (how i used to wash)
i hope this was helpful.