Back when cotters were SOP (an era lasting almost a century), most pros, and just about all non pros, installed cotters by hammer. It's an easy job requiring nothing more than halfway decent hammer skills (can you drive a nail without bending it?) and the awareness of the need to support the crank arm, which is the key to success. Testing the angle is especially easy with a hammer, because you'll only TAP it home (no need to support the arm yet), and can easily tap it back out undamaged.

For my part, I have never failed to remove a cotter cleanly and easily with a hammer. In most cases I could even get them out without damaging the threads.