You're asking the dads?
For my ex-wife and son, it was an emotional process. She'd cuddle him instead of nursing, I'd play with him during his usual nursing times. She phased out her nursing clothes, we switched to bottled breast milk and then formula. It happened slow and steady. He friggin' hated it, and we had to decide if we wanted a disgruntled misanthropic child with abandonment issues or a sheltered coddled child still on the boob when he's 16. He'll be turning 6 in a couple weeks and he's a sweet and gentle boy. If I have a second child, my advice to myself is to not worry so much about a fussy baby.
I don't know if that helps you at all, but it's what I can offer.