I regularly use a crescent wrench on the cam lobe, I just put a rag between it and the cam, works great and no issues yet.an old timer told be to do it, and I have no problem doing it.I would be more worried about damage done by putting a vise grip between the lobes, the cams are not great castings to begin with and adding stress points(the grooves left by the vise grip) would be a bad idea, at least as I see it.
theres just no way that i would ever hold the cam by the lobe.
however IMO i'm cheap
NEVER use the cam lock to hold the cam while loosening the cam bolt. There are lots of ways to hold the cam from turning. I've never used the vice grips on the cam or the crescent. Neither method appeals to me. It took me about 15 minutes one day to make a "temporary" pulley holder using an old piece of pipe, a piece of angle iron three bolts and six nuts. A drill and chop saw with fiber disc did the work. That makeshift pulley holder has lasted several years. I've actually just recently been eying some nice new steel square tube I have here and been thinking I'd make a more refined version. The actual tools can be had for $30 or so.