Filters all introduce a phase difference this is how they work. More importantly the phase change they introduce varies as a function of frequency across the signal. But again like Wetterberg says I'm sure we'd be able to help you better if you made your problem clearer.
Haven't done much with buffir~ personally but any delay will be of the order of a few samples but the filter works by summing multiple copies of the signal each delayed and scaled by different amounts. Therefore there is no delay you could add to your dry signal that would bring it inline with the wet. What exactly is the phasing issue your having? Could you post a patch that would be very helpful in sorting out what your problem is and how to solve it :)