I've found that pair programming for a bit can help me get past that initial resistance. It doesn't have to be anything special or official - just a shared screen with a friend over skype can be enough to get going.
It doesn't matter whether you are 2, 3 or 4 people. And it also doesn't matter whether you meet with a co-founder or a customer. It helps to meet in RL, but sometimes a plain phone call can be sufficient, too.