Originally Posted by PeterLYoung

I never remove the nut and washer just slacken it a little (say quarter to half a turn) then use the press every time the press pushes the nut down onto the crank slacken it a little until the cotter pin is ready to fall out, then completely remove the nut and washer. This way you are unlikely to bend the threaded section because it is supported by the nut. I have always found this to work, of course there will always be the exception but for me has been rare.