Lukaku was a revelation on-loan at the Hawthorns last season.
"Lukaku improved immensely as the season wore on," Brown told the Birmingham Mail. "That pace and power was always there,
"The one thing Lukaku has done is worked on his runs, when to make them, where to make them. It's also started to stick when it's been played up to him.
"Cyrille had he same when he first came. He had to be taught that he needed to hold it up and let his mates catch up with him so he could bring others into play.
"Lukaku is still young, he's only 20 - but his all-round game improved last season. You could see with each game he was learning something that improved him that little bit more."