I had the same situation at my home in Southern California, primarily fescue but some patches of bermuda. After treating bermuda with Roundup for a year and it coming up next season I chose to dig out the soil with the bermuda including areas beyond where bermuda was figuring roots were there. I dug out probably 18" deep of soil. Guess what? Next season bermuda back. I think once bermuda gets in a lawn you're screwed.

Actually it is pretty easy, just wiat until summer and use proper maintenance practice for Bermuda. Fescue will not stand a chance come June July and August. Then what ever is left hit with RU next winter when the Bermuda is dormant.

Yep, anything that grows taller than bermuda, is fairly easy to spot kill with Round up. I just put a little Round up solution in a dish, dip my fingers in there-and rub the tall grass blades with my fingers, making sure that it doesn't drip. If you don't want to get it on your hands, I guess you could wear a rubber glove.

Agree with all the above. Withholding water from bermuda is no problem at all for the bermuda. It can go for months with no water at all and awaken at the next rainstorm. Bermuda will not encroach into a dense stand of tall grass. Unfortunately fescue is not the kind of grass that grows dense. Kentucky bluegrass, on the other hand, might become dense enough to keep out the bermuda. You can discourage bermuda best by mowing the fescue at the mower's highest setting. I started with a bermuda mixed weed yard in 2014 and started to nurture only the St Augustine which survived around the shady spots near the house. St Augustine is a much more coarse bladed turf than fescue, so it provides much more shade to the ground. Today the St Aug has pushed out and filled in 40 feet away smothering the bermuda and other grasses.