That is an easy problem to cure. Use Roundup 41% 1/2 oz per gallon and mist over the top of your turf at about 1 gallon per thousand Sq Ft. It will act as a growth regulator on the Bermuda and control the sand spurs. It might take a couple of application at one month apart. No need to wait until it is dormant at this rate you will not stunt Bermuda enough to worry. As far as pre emerge for sand spurs Roundup will not work until the sand spurs have emerged. The Pre emerge you already used should help control that.