Dan Smith makes a good point. "A few" is not really a gradable adjective, it's more of an approximate number, like "a couple of" or "a half dozen." There's no way to compare "one few" to "another few." "A few" has no degrees and no opposite, but "few" does, the opposite is "many."
"Few," without "a" is gradable, and can be used with very: "very few people."
Note that in spoken English, the words "fewer" and "fewest" tend to be replace by "less" and "least." This is not considered "proper diction," but you should be prepared to hear it a lot.