I think dips/soaks/sprays are useful things to have on hand but one occasion where I do not use them is when fishing over any amount of free offerings. I think a Carp feeding on a bed of bait is moving from bait to bait sucking them up and gaining confidence as it goes. If it suddenly comes across this "different" glugged bait it may be enough to make it think for a second about what its doing and that could be enough for it to avoid capture.
As for taking one flavour but then covering it with something else, I do find that a bit weird. Why not just pick the flavour you want in the first place ? I dont deny it can work but I think most fish taken like this are caught in spite of, not because of, the extra flavouring.