Farhan, 40, said the 'Bhootnath Returns' star made him comfortable on the sets.
"I was anxious to know how the days would be with him (Bachchan). But it's very easy to work with him. He has a positive personality and keeps the atmosphere easy on the sets. So, the minute you reach on the set and start talking to him, you will feel comfortable automatically."
"It is amazing to work with him. I am still shooting with him as the film is not yet complete. It's great to work somebody like him and I am a huge admirer of his work. To get an opportunity to do a film, where we are spending a lot of time, is very exciting for me," Farhan told PTI.
The actor, who today unveiled a new mobile app 'Dulux Visualizer' for the paint company, is currently filming the Bejoy Nambiar's movie in South Delhi. He has put on weight to portray the character.
"I am playing an ATS cop and for that I felt being too lean will not look right. Whenever I meet them they are slightly tougher. I had to put on seven kgs for the film. I did power and endurance training and changed my diet to put on weight," he said.
Farhan met some of his ATS officer friends in Mumbai to prepare for the character.
"There are few people in Mumbai who are my friends. I did speak to them for few things like the training they go through before they become an ATS inspector. I also checked the posture and body language," he added.
Apart from 'Wazir', which was earlier titled 'Do', Farhan has also wrapped up the shooting of sister Zoya Akhtar directed multi-starrer 'Dil Dhadkne Do'.
This would be the third time the brother-sister duo have worked for a film after 'Luck By Chance' and 'Zindagi Na Milegi Dobara'.
"It was very nice to work with her. This is the third time we are doing a project and it's self definitive that how much we love to work with each other," he said.