Cana anyone recommend a plastic wrench that doesn'e scratch the metal?

As long as you have the correct size socket, any type would do. You just don’t want it to slip, that will cause scratching. Put the correct socket on the post and tighten with your hand, no need for a ratchet. AudioQuest has made this.

https://www.amazon.com/AudioQuest-binding-post-wrench-Discontinued/dp/B0009XQUAM/ref=sr_1_1?hvadid=77996669303746&hvbmt=be&hvdev=c&hvqmt=e&keywords=audioquest+wrench&qid=1575396695&sr=8-1

@dill that was the one I was looking at but the inside looks like metal?

It won't matter, if you have the correct size, it won't slip so it won't scratch.
Any socket will do, you just need the correct size. I used a socket many times.

@dill thanks!

Hand tight is fine.
If you have trouble with the connector holding, you may need softer connectors/spring loaded styles.

Very hard spades don't grip well.