I think hot rollers may be better than a curling iron.
I've seen hairdressers putting in hot rollers and then for the section of hair below the crown strategically putting in a curler and then wait a bit, they'd take out the others except for the one places below the crown. After a bit they'd take it out so it was a tight curl. They'd pin it up so the curl was just a loop and then tease and back comb the hair over to give you major volume like hers.