anonymous signature implementation and usage?
The first google-entry brought up this paper.
To answer your questions:


An anonymous signature is a signature that is unforgeable in the classic sense. But without the message no informations about the signer can be extracted from the signature even if brute-force of all public keys is possible.
If I'm understanding things correctly, a blind signature hides the message from the signer but the signer is still known. So the signer is not anonymous whereas with anonymous signing the signer is anonymous as long as the message is unknown, but the signer knows what he's signing. (I hope that makes sense)
The paper will give you insight in how to actually implement anonymous signature.


You may also wish to read this paper and maybe even some references to get further ideas. In the mentioned paper there's an approach the anonymize the signer by holding back parts of the signature.