During a long slow session of tantric intercourse, you can engage in a few different tools to enhance the immersion of the experience and accelerate the spiritual intimacy. This was mentioned in Practical Tantra but here I give some more details.
Aim for the following breathing pattern: as the man thrusts in, he exhales and the woman inhales, and then as his dick slides out she exhales and he inhales. Try to focus on maintaining this in a steady rhythm, and it will become hypnotic and meditative.
Also, first separately, have her close her eyes and visualize the sensations at her pussy as some light of energy, then gradually expand, slowly, detailing each part of her body as the energy grows. Ask her to make it vivid with color and feelings of warmth.
Once these have been well practiced, attempt to synchronize visualization with the breathing. Now imagine the energy flow from the dick inside her, up her body, then out her exhale as the man pulls out. and then into his mouth down his body, and then out his dick again.
This tantric energy cycle itself puts one in altered state, as well as primes you two for further sexual spirit connection.