The time it takes for Soto's Appliance + Porcelain Touch Up to dry largely depends on environmental conditions like temperature, humidity, and air flow but it will usually be dry to the touch in about half an hour. There are a few things you can do to speed up dry times, such as opening the windows (as long as it's not more humid outside) or turning on a fan. While one coat is often sufficient, if you're applying multiple coats, it is best to let the first coat dry for at least 30 minutes to 1 hour before applying the next coat.
Make sure it's fully cured (1-2 weeks) before scrubbing or using chemicals or cleaning agents on it. Paint that is fully cured (fully dried) is much more resistant to stains and wear.
Our suggestion when the repair is in a shower or some other place that will inevitably be exposed to water is to try to shield it from moisture as much as possible for a few weeks. The easiest way to do this is to take a piece of plastic like saran wrap and tape it on all 4 sides over the repair when showering. Remove the plastic wrap when done so the paint can continue curing.