Banner says "I put a bullet in my mouth and the other guy spat it out", implying that the transformation happened after he'd shot himself. So the transformation is definitely instantaneous.
Also, the biggest strength feat is definitely the one-punch take down of the mechafish.
Whatch Avengers again, those mechafish were so durable that they destroyed buildings by merely brushing up against them.
Hulk took down one with a standing punch and one when he leapt out of a building and dragged it down.
As for durability, Thor was noticeably running for cover when the jet began to unload on Hulk, yet Abomination and Hulk both can tank that kind of thing without a problem.
Kurse was bashing Thor, but that's nothing that Hulk couldn't have done (and indeed he was getting down to doing so, when the jet attacked him).
The physically strongest character here is Hulk, the one with the best endurance feat is Hulk.
I can't recall Kurse facing anything much aside from Thor's hammer strikes. The Asgardians were pretty feeble, no more worthy of note than the Dark Elves.
I'd definitely rate Hulk as superior to Kurse, from depictions so far.