Do your auto parts stores carry a terminal brush? I bought one 40+ years ago, it still works fine.

Has one part that fits on the posts, one the boes inside the cable terminals.

For the possible corrosion up inside the cable insulation, I have used the baking soda in water in a deep jar. Remove the cables, ALWAYS negative first. (Be aware that you may need a code to get the radio to work.)

Hold the jar far below the top surface of the battery, put the cable in and hold it until the fizzing stops. Do the other. Then refil with water and rinse thoroughly.

A single drop of the soda mixture into a cell will kill the battery. BTDT

Use the coated rings as recommended, red on positive.

Good Luck,

Bob

:>)