Is it necessary to clay bar each time before using a cleaner, polish, or swirl remover?
Also, if I apply paint sealant twice a year, after a clay bar, is it necessary to clay for the months in between, if I am only applying a carnuba paste?
I usually see a recommendtation to clay bar a car around twice a year (average person). I usually only do it about 3 times a year, but I would use it everytime I go for paint corrections. If your trying to correct your paint you obviously dont want any grit on there to get onto your pad and scratch your paint.
I always recommend the clay as a prep to any wax, sealant or polish process. Although there are some vehicles that just aren't going to benefit from the clay since it isn't needed.
Most of my polish services include the clay for the added benefit of the end result being the absolute best it can be. As mentioned above; most vehicles will be fine 1-2 times per year with the clay.