Joshua, 31, faces Usyk, 34, in a rematch of the bout that the Ukrainian won by unanimous decision back in September.
Usyk took Joshua's WBA, WBO and IBF heavyweight belts away from him in one of the biggest shocks in boxing history. .
It comes just a few weeks after Joshua was spotted visiting a number of different gyms across America amid calls to sack his coaching staff following the second defeat of his career.
Joshua was spotted linking up with his old pal Canelo Alvarez in the Mexican's adopted US training base in San Diego where he currently resides with cornerman and manager Eddy Reynoso.
AJ also paid a trip to visit Joshua Buatsi - who is part of his 258 MGT stable - at Virgil Hunter's gym in Los Angeles.
And now Bruno has revealed he is also willing to give some advice to Joshua in order to help AJ prepare for his trickiest foe Usyk.
“This isn’t the end of the AJ story. Sometimes in life you have to lose to win. I know that better than most," Bruno told The Sun.
“Anthony now needs to keep a level head, work hard and come back.
"I think he’s still got the fire in his belly and he’ll want to prove a few people wrong by coming back stronger.
"If I can help in any way I’d love to. He just needs to call me.
“AJ will also want to fight Tyson and prove he’s the best fighter in the world — but that part won’t be easy!”
Eddie Hearn has confirmed Joshua's rematch with Usyk will take place by April 2022 at the latest.
Speaking to talkSPORT, he said: “I think [the rematch] will be realistically end of March, early April.
“Both guys are probably resting, although AJ will be doing a bit more preparation because he wants to get it right.
“There was a well-documented trip to America, just to look really, look, learn and see. I think he will go back out there towards the end of the year.
“We will start talking to Team Usyk over the next couple of weeks and pin down the venue.”