Folks I flew back earlier this week from GRU. If you don't have to, don't arrive early. ALL the lounges I had access to (flying Polaris & Amex Platinum cardholder) were overcrowded and loud. Everything at the airport is overcrowded at night when most of the flights to the USA, Canada, and Europe leave. The check in areas are overcrowded, the restaurants are overcrowded, and I saw lines outside not just the Priority Pass lounges, but the Brazilian market credit card lounges.

As noted by some previous reviewers, the Amex lounge has the best food. The Banco Safra Lounge while less crowded was still crowded and full of people taking business calls well into the night. Honestly, find the seating in a gate not being used in the terminal and it will be quieter and less crowded. I think the one exception, from what I've read is the AAdmirals Club is less crowded, but alas I was flying UA so even if I had a membership, I was not getting in.