Nathan Green finished alone in third place at 6-under par. Gene Sauers, Robert Garrigus, Brad Ott, Travis Williams and five-time PGA Tour winner Ken Green were next at minus-5.
Hensby collected five birdies on his front nine, including a pair with long birdie putts at the first and second holes, before dropping his first shot to par at the 10th.
The Australian rebounded with three birdies in a four-hole span, starting at the 12th, to match his low round of the 2002 season.
'I got off to a good start with a couple of good putts on the first two holes,' said Hensby, who fired a 65 in the second round of the 2002 Omaha Classic. 'I've been struggling of late so it helps when you start making a few putts.'
Hensby, a two-time Buy.Com Tour winner who finished second in earnings in 2000, has made only one cut on tour since the Arkansas Classic in mid-April. He tied for ninth in Omaha earlier this month after his second round 65.
Winston recorded only three birdies on the front side but caught fire after the turn. He birdied the first four holes on Midland's back nine and parred his way in for his career-low round and a share of the first round lead.
'This really is a relief,' said Winston, who has made only three cuts in 11 starts in 2002. 'Today was the best ball-striking round I've had since this time last year. I'm just tickled to death.'
Tom Carter, Joey Maxon, Steve Ford, Brad Adamonis, Wes Short and John Adams were in ninth place with 4-under-par 68s.
Full-field scores from the Permian Basin Open