How to generate the revocation certificate after being made a revoker with GnuPG

Solution 1:

Do not use --gen-revoke, but --desig-revoke instead. From man gpg:

--desig-revoke name
       Generate a designated revocation certificate for a key. This allows a
       user (with the permission of the keyholder) to revoke someone else's key.

GnuPG will ask you whether you want to create a revocation certificate for this other key, for example revoking 0xdeadbeef with a key you're using:

$ gpg --desig-revoke 0xDEADBEEF

pub  1024R/DEADBEEF 2015-02-25 Alice

To be revoked by:

sec  2048R/E6F0D5F6 2015-02-25 Bob

Create a designated revocation certificate for this key? (y/N)

[...]

--desig-revoke will output the ascii-armored revocation certificate.