For seeing how gpg is used check out some of the contracts/assets, you can see berried in the xml is an xml contract that contains the public key and is gpg clearsigned.
http://dev.glbse.com/cgi-bin/list
(May need to view source if xml doesn't show)
http://dev.glbse.com/cgi-bin/asset?id=d59b25f04a13190c792c3e4199d44e4dce23abfb63729ab269c23d668dd22184.xml
Kiba, yes you could, but you would have to write it in such a ways as it's terms are something like:
The owner of this contract (that is the purchaser), may use this to redeem from kiba (include your gpg details and contact information etc.) the work stated below:
state exactly what you will do
GPG clearsign above text.
And you would then put that contract, quantity 1 up for sale on GLBSE for the amount you want to charge. and whoever buys it is the person you work for(it also means you get the money upfront).