It takes a while to work up to it. I got into the Fap Roulettes site. I play some of the challenges. It works me up to a point I dont think about it. The challenges also got me into taste and wear.
I'll never forget when a domme made me do this for the first time. After I came, I had no intention of eating it after I had already agreed to do it if I came. She basically forced me to do it. A deal is a deal. If you feel like you have lost the desire to taste it, just force yourself to put in your mouth whether you want to or not. Easier for me since I could think back to the domme making me do that, but maybe use your imagination of having a hot woman telling you to do it.
I was beyond my cum hangups early on in our marriage. During a seperation, I was with many different women. I would go down on them after fucking and cumming in them and always gave a thank you kiss. A few were surprised that I would kiss them or eat their creampie, but they all went with it, enthusiasticly.
My wife was good about cleaning up after I shot in her, just didn't like dirty sheets. But I went down on her many times after one or two goes and I'm sure she never got every drop.