We've had Cookie since she was 8 weeks old. She's now 6 months. Since day 1 we've told her over & over & over & over & over.... "NO!" NO BITING!!" We've tried sour apple spray on our hands, we've tried the yelpping thing when she puts teeth to skin, we've done the "NO BITING" and putting her away in her room thing... she's still the same, in fact maybe even worse. Now when we come home and she's excited to see us, she licks AND bites/nibbles on our hands. We can't even pet her without her trying to bite on our hands/fingers!
I don't know what to do. We would love to be able to pet and play with her, just for once without her BITING!!! Its so frustrating, we say NO, NO BITING in a firm voice, but she has never grasped it, even with all the tactics we've tried. I've even tried the whole... mother dog thing where, if she bit me or started, I grabbed her scruff, spanked her bottom and put her in her room. 15 mins later I let her out, she's happy and starts biting

.
She has ALL her adult teeth in now, so when she bites, IT HURTS!

Someone, anyone... any advice

??? I'm at wits end. Sometimes I feel like putting a muzzle on her cause I don't want one day for her to bite our 5 year old on the hand or face!