It's only like doing one-handed pushups if there's stakes to the conversation. So, remove the stakes and just contrive a fake scenario to practice openly/confidently stuttering in front of strangers! Call up a business on the phone and come up with questions you need to ask about their hours, or a product being in stock. Try it in person, and ask for someone to point you to the right aisle in Target. If you feel an incoming stutter, let it happen naturally without trying to force fluency. If you don't feel an incoming stutter, get some practice in by faking it. Build up to speaking situations that are longer, more conversational, or more personal. But you can practice your confidence using these quick interpersonal encounters on demand. They're strangers you'll never be forced to interact with again, so you may find it easier to be fearless in front of them because you're practically anonymous!