Well, you can try keeping something cool around, like an icepack that's only partially frozen so as to be cool but not so cold that putting it on your skin is shocking or unpleasant. If you feel subjectively that your temperature is a bit high you could then apply it to any area with major blood vessels – ie neck (where the neck meets the jaw, on either side), back of the leg behind the knee (like the crook of your arm but for a leg), a wrist, or even the groin area (not right on top of the equipment, but on the inside of a thigh where it meets the body, towards the front so as not to freeze what aught not to be frozen). Those are all areas with to a of veins and arteries, so applying some form of cold press to such an area cools the blood, which then cools you faster than if you just simply put the cold pack on your skin wheee-the-fuck-ever.
Or you could try a cool shower. Showers are amazing on psychedelics just by themselves without any other uses. But I think rather than trying to address the symptoms you should try to get at the cause. By this I mean that the sensation of being overheated is likely psychosomatic, where the brain imagines that the body is feeling something. Obviously considering the state of extreme susceptibility to suggestion (whether said suggestion is initiated by another person or by yourself) that you are in while tripping the ability of psychosomatic symptoms is not that surprising!
I would try and think about why you don't experience this symptom in a group, both before dosing and while waiting for the come-up. I would venture that you're simply very distracted from your body and how it may or may not be feeling by the social situation when tripping with others. So I suggest trying to ensure that your mind and more over your attention are constantly engaged during the trip. Also, if you feel too hot, take a short period of time to simply lay down and relax yourself with closed eyes and enjoy the resulting visuals, I bet this will help wonders.
The other thing I suggest is that you practice the technique of telling your body and brain to settle down, as in telling your conscious and unconscious selves that you're simply tripping and it's the drugs making you goofy, and that the drug you're currently tripping on will no longer affect you in only a few short hours (ie once you come down). Also try and differentiate between sensations: the body buzz on 2C-B for example DOES make you feel like you're hot. But if you concentrate and block every thought from your mind save those related to contemplating the body buzz and its associated sensations, you will find that when you really pay attention what felt like heat is not heat but rather simply a component of the body buzz that could easily be mistaken for warmth if you don't pay an exaggerated amount of attention to it.
And finally in the same vein as learning to tell your body or mind to chill / learning to differentiate feelings similar to a given sensation from the actual sensation itself, I suggest that if all else fails and you just feel totally too hot, go get an under-the-tongue thermometer. Sit down and do that relaxation thing I mentioned in the first paragraph for a minute or two so as to not get a reading altered by a momentary increase in temperature from moving around. Once one or two minutes have passed, take your temperature. I bet it will be within the normal range for your physiology. This above all else would be my fall-back position were I you, but one that I imagine could be very effective indeed! The reason I would use this as a last resort is because if the symptoms are psychosomatic, as I believe they are, then the ideal / most-effective treatment will also be psychological / mental. There's absolutely nothing wrong with going straight to the thermometer and ignoring possible psychological or mental solutions to the issue if that's what you decide is best for you. It's simply my own personal position / opinion that psychological cures are best for psychologically-induced ailments. I figure it doesn't cost one anything extra to try to fix it mentally first, so that's where I'd suggest you start!
