Chiles are self pollinating.

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Chiles CAN self pollinate (many plants reject their own pollen), but the mechanics of the flower means that bees help a great deal in the pollen transfer. Whenever that happens the flowers own pollen will be in great abundance (more so than other pollen sticking on the bee's body) so most of the seed will still be self pollinated. If bees are not around, vibration from the wind etc produces a little cloud of pollen in the air around the flower and that can stick to the stigma of that flower. The fruits will be entirely self pollinated then.

So, if you are growing plants side by side you will have some percentage of cross pollination if you have sweat bees or bumble bees around.

A day or so after the flower opens, I take a q-tip (or the tip of your pinky finer) and very gently rub all of the currently open flowers. I do this once a day pretty much once the buds start opening.

I grew my first Bhut's last year and wanted to do the same thing ,(keep them true) Then Both side neighbors grew peppers in their gardens bordering mine and blew my plan :( Anyhow,I have successfully overwintered 7 plants with very little effort. A severe prune,top and roots .Then bring them inside.
Point being,The true plant will always produce true peppers.