I’m in a different boat in certain ways, as for me stuttering is triggered by anxiety (primarily social anxiety). Like you, certain days I can manage to hide my stutter - in conversation, I do a ‘reset’ of sorts by pausing and taking a deep breathe. I like that idea of covering your mouth you mentioned, because when I pause to breathe, people can sometimes not understand what’s going on if I take too long to reset to get a word out. Certain periods are worse than others, though, and it’s really frustrating to know when you’re in a bad period and your usual techniques aren’t working. At my worst points, it sometimes help if i focus less on breathing and instead focus on slowing down. Doesn’t always work, but psychologically it can help to think ‘I’m going to talk really slowly and carefully, and too bad if people find that too slow’ because I pretty much always end up talking at a completely normal speed, and end up coming across more comfortable.