It will polish up wet sand it 1500 then go over it with 2000 you ll need a buffer set it around 2500 that g3 stuff isn't great IMO better with 3m compound used a hard pad and a hard compound then go over it with a soft pad and a finish compound and you ll get a really nice shine .

The cold has nothing to do with the lack of a shine by the way it was probably just put on to dry