Gibson is supportive and understands the battle ahead for Guildford after the new NSW coach lost his sister Kiri to alcoholism earlier this year.
Guildford linked up with the Waratahs last week as they began pre-season training. Gibson said he had been one of the side's best trainers so far.
"The pleasing thing is Zac is trying to be a better man, to make better choices," Gibson said on Tuesday.
"In terms of rules and so forth it is a bit like a pre-nuptial, Zac knows very clearly of the boundaries we have set for him, making sure that he protects the team at all times.
"He is very aware of that and so far he has been brilliant." Gibson was encouraged by Guildford's honesty.
"He has made a bold, courageous statement that he wants to stay away from the drink," Gibson said.
"I have been personally touched by addiction, I lost my sister to alcoholism and she was only 44, I really understand what he is going through, just how devastating addiction is in terms of the ups and downs and the families and people close to them go through.
"The great think about Zac is that he is an honest person. He has come out and shown everyone 'this is what I want to do' and I want to support him."
Guildford said he had used his father's death due to a heart attack while watching him play in the under-20s championship as an "excuse" for his drinking.
It has contributed to an number of disciplinary issues. Just last month he was stood down by his provincial team Hawke's Bay following a binge after their Ranfurly Shield loss to Waikato.
"I know how hard it's going to be (not drinking) but I don't want to live the life I've been living for the last six years because it's been pretty average," he said.
Gibson was coaching the Crusaders when Guildford was coming up through the ranks and said the winger could still return to the heights that earned him 11 Tests with the All Blacks, the last in 2012.
"I said to him you are going to have to be the best Super Rugby winger in the competition for the All Blacks to even look at you again," Gibson said.
"So he is very focused on going through that process toward become that type of player."
Guildford has signed a 10-month contract with the Waratahs. He last played Super Rugby with the Crusaders in 2014.
-AAP