The best way to go with hairless is to breed the hairless father with a furred mother. This basically creates babies that are furred, but het for hairless. Then you breed the furred females you get to either the original hairless male, or get a new hairless male to expand the gene pool a bit. You should get 50% hairless in the litters then. The females with hair are less likely to have the issues the hairless females do, but can still kick out a good number of hairless babies.