Gainey, who began the day a stroke behind Hend, paired eight birdies with two bogeys to improve to 12-under 134 at Royal Golf Dar Es Salam.
The American is a stroke clear of Hend (69) and South Africa's Darren Fichardt (65) at 11 under.
Hend opened with a triple-bogey seven on the first hole before making seven birdies, an eagle and two bogeys for a four-under finish on Friday.
Gainey is seeking his second PGA Tour Champions title since becoming eligible for the tour last August when he turned 50. He entered the week 11th in the Charles Schwab Cup standings, but would surge into third if he holds on to win in the final round.
After a two-under front nine, Gainey started the back nine with three straight birdies on Nos.10-12. He followed his lone back-nine bogey at the par-3 14th with consecutive birdies at the 16th and 17th before saving par on the final hole.
"I'm hitting my driver really well," Gainey said. "As I said yesterday, the only difference between today and yesterday was hit a couple bad shots with the irons. Yesterday was a lot more flush.
"Today I hit a couple bad shots with the irons, but in saying that, the putter was just as good or better and the driver was just as good or better. So if I just keep hitting fairways, greens, make a few putts, I've got a chance."
Fichardt had the best round of the day, finishing a bogey-free front nine at four under before following his lone bogey at No.11 with an eagle at the par-5 12th to make up that lost stroke and then some.
Fichardt, 51, has won five European Tour events and one European Senior tour title, but is seeking his first Champions Tour victory after never winning on the PGA Tour.
"I just played really, really solid. The greens are so severe, your second shots to the green, you just hope you have an easy enough putt. Luckily, I had a lot of opportunities," Fichardt said.
"I suppose this course is definitely one you play one shot at a time, not get ahead of yourself, not think too negative because if you get in a bad spot, it can catch you, you can make bogeys very quickly. So all in all, played really solid."
Jason Caron (67) and Australia's Greg Chalmers (68) round out the top five at eight under and seven under, respectively.
with AAP
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