i've done both... and honestly, the old baseball bat method is a lot easier. just put the car in neutral, wedge bat between tire and fender, and jam bat up in there while pushing the car back and forth by hand. The tire sidewall will give a little so its not really as difficult as you'd expect. Just roll it back and forth a few times... and see what you think.
You can never guarantee that paint won't crack, even with the fancy fender roller tool. But most cracking will be on the inside and you won't be able to see it. I'd cover it up with some paint tho to prevent it from rusting.
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4224479: 74 2002, #74 EP/FSP, daily driver
I beat my car like it owes me money!