I just did this to mine which is now 8+ years old. Buy new filters online do not clean the old ones = useless which BTW, do not have to be from Dyson. Surgically disassemble entire unit including motor. Prolly should take pics as it is deceptively simple but complex. Inspect the upper V- thingy tornado chamber and the most nastiness will be found there.

I used soapy hot water to back flush top / bottom and then shop air and took some time until there were no dirt / hair /debris left in sight. Same for all other orifices / tubes. Then let air dry for 48 hrs. Now good as new!!