Police added that officers have trawled hours of public and private CCTV footage as part of the investigation, while door-to-door enquiries are also continuing.
The last sighting of either man had been on Friday morning.
Police also said the Chancellor Street property where the bodies were found was the home of one of the victims, and that the two men knew each other.
Det Supt Cheryl Kelly, of the force’s Major Investigations Team, said: “I am appealing directly to anyone with any information, no matter how small or insignificant they feel it may be, to come forward and speak to us.
“Please do not assume that the police already know the information you have.
“We are keen to hear from anyone who knew Paul and Gary or who was in the Partick area near to Chancellor Street from Friday morning from 09:00, who saw Paul or Gary, or saw or heard anything suspicious.”
Supt Craig Brady said: “I would like to extend my sympathies to the family and friends of Paul and Gary as they try to come to terms with their loss.
“We understand the significant impact this will have on the local community and I would like to thank everyone for their help so far.”
Post-mortem examinations took place on Monday and Tuesday and confirmed the causes of death as being murder.
A major incident public portal has been launched, external as part of the investigation.