johnoink ... I certainly can't speak for everyone . When you talk about preventing cross pollination I'm sure you mean you would like to get "true" seeds for the next season. Some people get peppers that they like ....taste , shape , heat , yada yada from the deepest part of their plants. They use those for seeds. And if you have a large variety plants that's the simplest way. You hope the wind or Bees didn't pollen in that deep.
The only way to be sure is distance for isolation or closing off some pods. You can make " tea bag " type of things to cover a few pods . Or you can make a sleeve type thing which would be bigger , but maybe easier to work with , and cover a whole branch with several flowers.
Peace ,
P. Dreadie