Most of the time, dabbing leaves some residue on the nail, which is harsh and doesn't taste good. The flavor of the extracts is one of the main reasons people like to dab; After every dab, many people use a Q-Tip to swab the bottom of the nail with a Q-Tip to get a fresh, great-tasting dab every time.
Use one end of a Q-Tip to remove any oil from the nail after taking a dab while the banger is still warm. Then, flip the Q-tip over and wipe the nail once more to check for any remaining oil. One dry Q-Tip ought to suffice if you are dabbing correctly and at the appropriate temperature; there should be very little oil and no char.
You may need to dip the Q-Tip in some isopropyl alcohol to help remove any char or tough spots. The alcohol will quickly evaporate when you heat the nail again.