Excellent opportunity for you to try some role playing.
Purchase yourself a large dildo (it doesn't have to be enormous). Take on the permisterna of a bull, disguise your voice, and manipulate the sexual intimacy a little more powerfully than what you would normally do. When the "new bull" is finished with foreplay, fuck her with the dildo by holding the base of it against your lower torso (as if it were your own cock). Let phrases slip out like, "Too bad your husband's cock isn't this big", and "You deserve to be owned by a Big Cock Bull".
Watch for the tell tale clues that really turn her on and make her cum, and progress from there.
You should be able to easily figure out if she really gets turned on by your "new bull permisterna" and you can progress from there to the real thing when she is ready.
You'll have to be the judge on which dildo to buy to satisfy your wife.
My wife is extremely prissy and sensitive. Any dildo with veins, ribs, a large head, or whatever irritates her pussy and soon spoils the mood.
After spending hundreds of dollars on dildos she settled on this one, it really makes her squirt -
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Good luck and keep us posted on your progress!