I had a pair of pruning shears in my hand and my son was holding my MEAN roo so I just took advantage of the opportunity and trimed his spurs. He didn't seem to mind so I trimmed again only deeper and this time he let me know that I had gone too deep.
There is another method that I saw yesterday where by you grab hold of the spur with a pair of pliers and gently twist the spur and pull and it comes right off and leaves a small soft bloody stump. Looked easy and painless.
I use a dremel tool and cut them off with the cutting wheel. You need to have someone hold his leg very still, but it cuts through and cauterizes it at the same time.