Wheel woolies would definitely be a good investment. They won't damage your rims and they just make cleaning wheels so much easier/faster. I like using the small one for getting in between the spokes and the big one for the barrels.
There are a few real 'Wheel Woolie' branded ones, but they are all around the $50 range.
Don't fall for the trap of purchasing the ones that are half-price. The real wheel woolies are very high quality and you definitely get what you pay for.
We have tested the cheaper ones made in China and they are definitely not worth it.