Posted this in another thread:
In my experience the most thorough way to clean a DAT deck is by use of denatured alcohol and foam swabs. Avoid cotton swabs as the threads in it will easily displace onto the drum and heads. It helps to power on the machine, open the tray, shut it off and then start cleaning. And unplug it just to be on the safe side. Take a foam swab and dip it into the denatured alcohol, squeeze out the excess inside the can, and then with one finger hold the top of the drum in place, and then put the swab against the drum. Move the drum with your other finger in a clockwise fashion while keeping the swab in place. Check the swab for any discoloration, if there is, flip the swab over or use a new one. Go through a few rotations and clean any metal the tape comes in contact with. Avoid touching any rubber. Make sure the whole mechanism is dry then put the cover back on.
This works the best IMO. The dry cleaning tapes seem to be OK but I feel more confident knowing that I cleaned it and I saw it get cleaned with my own eyes.
Also important to note is use good quality swabs, and not something that will deteriorate when it comes in contact with the denatured alcohol.