Priming and Blowing fur
Chin 'blowing fur' while priming
Chins prime for the first time between 6 and 12 months, then around every 4 to 5 months after. You can check for prime by blowing into the fur and looking for a bar - if the chin is in a perfect state of prime you will only see one bar. If the chin is out of prime, you will see the new fur (and bar) coming in - as well as the chin tends to have a more 'choppy' look.
Chins will also ‘blow’ fur during this time – it is normal and you will see it happen with more densely furred chins. You can comb them or pull the lose fur out with your fingers.
Above - Female (literally) halfway primed out.
Below - Priming lines; chins prime in different places at different times.