I use this:
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I thought about using them but then my bends could be inconsistent, when you have to do 28 carsides that can get tedious and my forearms will be huge! Additionally it will mar/scratch the polished plating on the carsides.
The S.
I would use what The Master uses.
As far as hurting muscles, you should take up blacksmithing; swing an eight pound double sledge for a few hours a day and see if that doesn't beef you up. It isn't expensive, either, once you get a forge (I use a fire truck brake rim, solid cast iron, and can be had for under ten dollars), a set of ball peens, a cross peen and straight peen, four pound sledge, and an anvil. The most expensive part was the anvil, and that's going to be a dollar a pound or so; mine is 150 lbs. For under three hundred dollars, you have everything you need to get started; any other tools you may need you can make.