Mastubating prior to a session might help. Using a thick condom would reduce sensation too. There are numbing creams, but not sure you would want to get any of that on her fun parts.

that are designed to get you to become accustomed to the sensations that lead up to ejaculation.

For me, this consisted of masturbating until I was close to coming, and then stopping completely.  During this period I hold my breath as long as I can while centering my focus on my body.

Repeat this many times for as long as you can, and with time you will learn to control when you come.

Seeing a good and skilled tantrika is also a good way to learn to do this.

Here's a link to a site with many good tantrikas.  Maybe one will be in your area.  There is also a wealth of information about tantra if you want to learn more.

When you feel you are about to climax, pull out and either you or your companion should grasp the base of the penis tightly and hold, about 30 seconds, before resuming.  Then restart.  It's supposed to work!

Caveat: I have not tried this; only read about it a few places.