Most of the records I buy now come from auctions or flea markets, so a portable player doesn’t help much. I rely on things like the label design, group/artist names, song titles, appearance of the wax, matrix numbers, and the like. That way I can weed out a lot of the bad ones.
Stopped going to record shows years ago as my interests changed.
But, yes, the portable player is an essential tool.
The whole thing started for me because I really liked the music, and prices were still very reasonable. I was able to routinely buy records at shows for a few dollars each which are now worth hundreds. Unless you get lucky, you won’t find buys like that at record shows any more. It used to be fun, but once the supply dried up and prices really started to soar, the fun went out of it, and it became a money chase. It stopped being a hobby.