Once you get your sheets up you have to tape and «mud» the joints with drywall compound. (moneysense.ca)
Bliss, I agree that mixing paint in with premixed drywall compound would be tough. (theshabbycreekcottage.com)
In a plastic container (if it has a lid it will last a week or so after mixing), mix together 1 part drywall compound to 4 parts paint. (theshabbycreekcottage.com)