You are arriving international and connecting domestic. You will need to claim any checked bags and go thru customs, then recheck the bags. This will put you land side. When you go to T2, there are several lounges, some which you can access via Priority Pass or AmEx Platinum in addition to any airline FF program. I found the GOL domestic lounge to be pretty nice. It used to be the United lounge prior to T3 opening. There is a walkway between T3 and T2, but the last I heard it had been closed for some reason. (
Changing Terminals at GRU for Connecting International Flights, Sao Paulo ) Even if it has reopened, you would go thru security to use it and I don't know if a boarding pass for a T2 gate would allow you access to go to T3.