I'd just pass on contact cleaners. One of my jobs before I retired was to test them along with lots of other materials hyped by tons of salesmen with wild claims. They would typically get to a high ranking person at one of our customers, who would then ask our opinion, and we needed a technical response. The best ones did not cause any harm, but were not really worthwhile either, so we gave the customer the test results and told him that we did not recommend their use.
One thing of concern is that cleaners are solvent based, they dissolve grease and oils. Those contacts in a TC are spring loaded and have lubricant to keep them from sticking. The lubricant is on the hidden springs and should not be visible, but using a solvent based contact cleaner can dissolve the lubricant and flow it into your lens, mirror, sensor, mirror box, places where it doesn't belong. It can spray out thru piston action when you attach to the lens or to the body and the contact is depressed.
I'd recommend avoiding contact cleaners.