Exes Christina Milian & Lil Wayne Are Still Grinding (PHOTOS)

Christina Milian and Lil Wayne still have their hands all over each other, a month after their break-up ... but it's all in a day's work.

Wayne grinded with a barely dressed Christina on the set of her new music video for "Do It." The video was shot last week in Miami and judging by photos it's hard to believe it's more business than pleasure.

Still, sources tell us they aren't getting back together, but remain friends ... so working this closely is not a problem. We're told the chemistry will always be there.

Easy to see why ...