A: You can just pick up where you left off each time it happens and do your best. Be gentle with yourself and try not to stress on doing every single thing perfectly. With time it will get easier, and also every effort counts toward improved health.
A supplement that you can take when you have been “glutened” or have had dairy but didn’t mean to is Gluten/Dairy Digest by Pure Encapsulations. This supplement is not something that you would want to be using in order to eat dairy/gluten, but it’s useful if you go to a restaurant, for example, and they don’t have a dedicated kitchen for dairy/gluten free. Then you can take it to help counterbalance any cross contamination.
Another thing that can be helpful to reduce inflammation is taking Systemic Enzymes. Also, having some bone broth to allow some of that inflammation to cool down. Butyrate can also be helpful for lowering inflammation in the gut. Here is a guide from my Gut Recovery Program called What to Do if You've been Glutened, which can be helpful.