So, this is what you're aiming to do

It's been quite some time since I posted anything here. I've been very distracted so I really haven't dedicated time to things related to aneros, but I got to be pretty good with it at some point. Anyways, I wanted to explain a couple of things and see if they can help you.

First of all, proportions. I'm convinced that women have the perfect design to be able to enjoy lots of sexual stimulation, but it's not only that, because their approach to sexuality is very different to ours from the base. So, if you think of it, their "main" sexual organ, the one that uses up more space is their vagina, while the clitoris uses up a very small percentage of the volume. We are kind of the opposite, what could be thought of a vagina, which is the rectum with its very own g-spot, is very small in comparison to the penis. The penis is the "main" organ in us.
What you have to do is revert that, you don't want to make the penis your main focus, you want to make your rectum including your g-spot and anus your main focus, as though it was your main sexual organ, while the penis, still participating, should be only used as an accessory, not as a tool. In other words you should pay attention to the penis, only for sensing purposes, but not used for forcing purposes (much like a clitoris).
There are a couple of things that may give you a hint to know if you are doing it right. Whenever you make the penis your main sexual organ, you are almost constantly "spending" sexual energy in pleasure. You get pleasurable sensations right away, but if you keep doing it, you are guaranteed to ejaculate after a while, getting a "dull" orgasm. When you make your rectum and g-spot your main sexual organ, it feels as though you are refraining from pleasure. If you let things go "naturally" you'll feel that sensation will tend to fall and accumulate on the penis, which will feel pleasurable, but you are letting it leave you instead of building it up. What you are doing here is holding that sensation back to your rectum and g-spot. Get the idea? You are holding something, letting it build up, not spending it right away and letting it go as soon as possible. Sensation must start with your rectum and g-spot, and instead of letting it go towards your penis, you keep it there, holding it. Remember, it feels like refraining from pleasure, but it's not like being in a non sexual context. You are actually holding in place something that wants to go away as fast as it can, more and more as it accumulates and grows.

Your penis will tend to get more sensitive, most likely triggering an erection. This is kind of hard at first (no pun intended) but with practice it gets easier. When that erection starts happening, if you keep "holding" it, your penis will get erect only half way. You must be able to stop that erection before it happens at 100% and lowering it until ideally it's less than 10% erect. You are overcoming the temptation to squeeze and make that erection happen by holding it back and not forgetting that your main sexual organ is your rectum and g-spot, not your penis. Your penis is just there to feel things, not to force things.
Basically, as long as you keep that approach in mind, which is to make your rectum, anus and g-spot your main sexual organ, by not letting your sensations fall to your penis, you are going to be right on track for the super-o. Just keep in mind, your main sexual organ is your rectum, anus and g-spot, your penis is just there as an observer, though still participating.

So, whenever you are planning on starting a session, as soon as you are decided to do it, you make your rectum and g-spot your main sexual organ*. If your penis starts getting cold, you are doing it right. In fact, try to keep it cold for as long as you can when doing this by focusing on your rectum and g-spot. Whatever you normally do with your penis, in terms of how much attention and forcing you put into it, feel free to do it with your rectum and g-spot. Never letting the sensation go to your penis. I say this because you'll want to let things go to your penis, you are used to it.
When you hold the sensation, as it builds up, you want to get in touch with the rest of your body. Feel your spine, your head, etc. Instead of releasing all that energy that's been building up on your main sexual organ (rectum, g-spot and anus) to your penis, you are focusing on the rest of your body so that it will follow.
I could explain lots of things from here, but really all that you need is to keep in mind that: Your main sexual organ is your rectum, g-spot and anus.
As long as you stick to that approach, and explore every other possibility without focusing on your penis, you'll deffinitely start making lots of progress at some point, once you really "get it". You are receiving, keeping and holding (in your rectum), not generating, letting it go away and spending (through your penis).

How do you make those your main sexual organ? By feeling them. Learn to pay attention to those parts, feel all the subtle sensations they give, try every possibility always keeping in mind that you have to able to get a feedback in terms of sensation.

*In fact, it really doesn't hurt to do it throughout the day whenever you remember it, even if you are not planning on having a session later.