another old trick was using a pencil eraser on the gold contacts. I would leave Brasso to the absolute, final, "nothing else worked" last resort.

FYI, these a company has a bunch of new cleaning products on Amazon. Check out using something like this: https://www.amazon.com/1UPCard-Mini-Card-Pack-Game-Boy/dp/B07D716ZM1/ref=pd_bxgy_2/140-8388405-3876669?_encoding=UTF8&pd_rd_i=B07D716ZM1&pd_rd_r=4d04d0ad-6db5-11e9-9c58-2d5da5e59492&pd_rd_w=hoRxE&pd_rd_wg=N1StO&pf_rd_p=a2006322-0bc0-4db9-a08e-d168c18ce6f0&pf_rd_r=QFA5Y1YFMF1RR3BZW6R3&psc=1&refRID=QFA5Y1YFMF1RR3BZW6R3