Armpits? Call me old fashioned, but what's wrong with titty "outercourse"?
Alive and well, brotha.
Step One Straddle your female partner with your knees wrapped around her upper body and chest. She should be in the most comfortable position possible.
Step Two Apply lubricant to your penis and your partner's cleavage. The constant skin on skin friction of mammary intercourse can be uncomfortable for both of you if you don't lube.
Step Three Cup the breasts around your penis and pushing them together tightly without hurting your partner. Thrust back and forth with your penis. To increase the stimulation for your partner, caress her nipples. If desired, the woman may hold her own breasts together, helping to stimulate you sexually.
Step Four Adapt mammary intercourse in a variety of ways for heightened stimulation. For instance, your female partner may place her head on a pillow or lift her head gently and perform oral sex as you continue your thrusting motions. You may also hover your partner's head, facing towards her feet, and perform mammary intercourse while she stimulates your anus with her tongue and lips.
Step Five Communicate with your partner as you approach ejaculation. Some women may not enjoy the experience of receiving ejaculate on their faces. You can ejaculate between her breasts, on her face or neck, or even in her mouth if she so desires. You may also end mammary intercourse by removing your penis from her breasts and finishing on another part of her body.
http://www.ehow.com/how_2155782_have-mammary-intercourse.html