I use a bronze two pin wrench, on side fits the Groco strainer, the other side had larger pins. It comes in handy for the fuel caps and the floor spin on hatches.
I was going to buy a special tool until I tried a crescent wrench.
Use a larger wrench. Put the hole in the handle over one of the cap posts and use the side of the wrench for leverage.
Unless the top is frozen it will come off easily.