I did use EMLA, which is a prescription cream, but it was not for my sensors. I used it prior to chemo treatments for the port site. I put it on just prior to leaving my house, so it would have been closer to an hour by the time the IV was poked into my port. And they always cleaned the site first.
So I agree with Maria, regarding the wait.
AE13 mentioned alternative, which I believe is not Rx, since I saw it on Amazon. I think the AZ product contains only one of the 2 ingredients in EMLA, but may be just as effective.
And good news… I understand the next generation of Dexcom sensors will come with improved inserter, spring loaded instead of manual push.