Every March when she's shedding I brush and comb my lab. I've got a big bag of the hair and it makes an outstanding dark brown/near-black dubbing.
I wash it in a big mixing bowl of soapy water, rinse it in a tea strainer under the faucet, then dry and bag. No need to chop it in a blender.
Know someone with a lab? Offer to give it a good brush and comb job (and be sure to bring along a couple large ziplock bags).
Excellent dubbing...Mike T is right on the money here. Back before packaged dubbing became widespread, a tyer named Polly Rosborough (read his book TYing and Fishing the Fuzzy Nymphs if you can find it) suggested that a good source of dubbing was the local pet groomers. If I remember correctly, he got a lot of his dubbing there. Dog hair dyes well, as I recall, and with a yellow Lab, you've got a more tying material than you're likely to use in a lifetime.
I'm trying to remember if I ever had a problem using hair from my Lab. I don't recall it, but then I tend to prefer buggy looking dubbing anyway. As an example, I don't pull out the guard hair from mink or muskrat. I really don't recall if the longer guard hairs on a Lab were problematic.
Now, if you're looking for really smooth dubbing, get a cat. Short-haired cats have really fine dubbing fur.