Want to adopt a cat, but I have allergies. Anything I should look for to find a low allergen cat?

I know that certain breeds like hairless cats and the Cornish rex are considered hypoallergenic, but I'd prefer to adopt a cat rather than go to a breeder. Is there any general consensus on things like coat length, colouring, sex etc and how they affect the how allergenic they are? I know with shorter haired dogs, they are typically more allergenic as they shed more frequently - is this the case with cats?

I intend to brush my cat regularly (if they let me!) and get an air purifier. Any other tips people could give me?