The bench vise sounds like a good idea and was probably quicker than my approach.

I used a socket and c-clamp to remove one of the cotters on my old Raleigh but sprung the c-clamp on the second. So I just took a break from the bike work and made myself a cotter press. It's only been used a couple of times but has performed flawlessly on two different early 70's Raleighs so far and cost me nothing but a little time and scrap material.