You cant avoid co2 build-up, you can only slow it down, main factor here is relaxation. Particularly your brain needs loads of o2, so if you can keep that calm it helps a lot. Obviously a slow metabolism helps as well, so before big static performances fasting is common.
And regarding co2 tolerance, it is a training effect. With training you can withstand much higher levels of co2 without resulting in panic
And co2 build up isn't even that dangerous, just really uncomfortable. Lack of co2 (from hyperventilating) actually inhibits oxygen uptake and causes dizzyness (up to passing out) that way