A summer of promoting his policies nationwide would be a good start
Could you tell us what the policies are?
Not Trident: Labour policy is still renewal, and he needs to go to conference to change that. He'll probably lose, but we'll see (I'm not bothered either way, like most people).
What about Europe? He could campaign on his long and noble history of supporting the EU and make it clear that Labour are committed to reducing the damage of Brexit. Ah, except about that "long and noble history of supporting the EU"...
What about some economic policies? He could get his advisors like...oh, he's resigned...oh, and him...oh, and him...well, never mind.
Maybe education? Perhaps he and Diane and Emily and Seamus and Harriet and all the rest could unite and try to promote Labour's policies on comprehensive education? Well, for the proles, at least: their own children wouldn't be seen dead anywhere near a comprehensive school, of course.
Could you suggest some policies Jeremy has which wouldn't invite open laughter when promoted? Does he have any?