Bruce Banner hears that Doom has an answer to Hulk, by teleporting to a place where his enemies are too strong for him. Instead of confronting Dr. Doom right away, he prepares Hulk for two days for an enemy he can't beat. While doing so, Banner finds a celestial armory in the things he steals from Doom's castle, Reed Richards labs, and Apocalypse tomb. He was planning on more when Dr. Doom transported Bruce to Metropolis, somehow transforming him into the Hulk on the way. And you already know how the cookie crumbles when Hulk decides to come smashing. Luckily for Hulk, his Banner prep helps him whoop the man of Steel's @ss. Deciding he can't beat Hulk on his own, yet not wanting to go to the jla (who are all on vacation at the time), he goes to Lex Luthor. The duo prep for the Hulk, while Banner now having more time to himself, preps for his next encounter against Superman.
Win By Ko/ Death
Banner has 5 days prep. 2 with no knowledge on his opponent, 3 with knowledge only on Superman
Banner has celestial tech to work with while prepping.
Duo has 3 days prep, with basic information on Hulk (No knowledge on Hulk's energy source)
Battle takes place in Metropolis