See the comment just above yours on combatting force frames. It's actually pretty straightforward... but you are generally safe using force frames yourself, since almost no one combats them.
As far as learning frame control... hmm, good question. I should probably do an article on that. Added to my article queue.
However, to start, I'd say ask yourself this.
Let's say someone challenges your frame. Let's say he says something ridiculous, like "Hey John, you are a beetle, not a man!" do you:
Think "Maybe he has a point... I do not act very manly. Maybe I am kind of beetle-like"? Or do you
Not actually feel threatened in your masculinity at all, but you don't confront the guy because he seems kind of tough and you'd rather avoid the fight, or avoid losing the frame battle and looking even more foolish?
... because whether it is the case that others' frames cause you to have moments of doubt, or others' frames do not cause you doubt but you just prefer to avoid confrontation, your remedy will be a little different (or you might have some of each of these: sometimes some doubt, sometimes confrontation avoidance).
To deal with doubt, you need to drill yourself in the habit of "Anyone who critically attacks me is wrong." (constructive criticism is fine, but if there's at all a status jockeying element to it, it's hostile, and therefore wrong) Every time someone attacks and you let it slide, analyze it after the fact and say "That was wrong, I shouldn't have let it slide." Do this enough and you'll stop letting it slide when it happens.
To deal with fear of confrontation, work your way up with smaller confrontations. Even things like asking for things if that's scary. Ask the waitress for stuff you feel uncomfortable asking for at a restaurant. Get better at asking for compliance. Go out of your way to disagree with people and get comfortable at that. As you go along, you'll find it easier and easier to hold frame in all sorts of scenarios. Continually challenge yourself to hold frame in tougher situations.
Same deal with insecurity. Just keep putting yourself in uncomfortable situations and do your best to stay in control. It's like lifting weights... you start off with spindly arms and can barely lift any weight at all, and everyone can tell you're a shrimp. Keep going to the gym, and you slowly build strength, put on muscle, and improve. After a while, you're pretty solid. Stay at it long enough and you may reach the point where you're one of the bigger guys there.
Frame control and insecurity are two sides to the same coin, really. As you work on one, you work on the other.
People have different emotional profiles. Some people are naturally pretty insensitive to what others think of them, which makes frame control easier and insecurity less a problem. But being sensitive and acutely aware of how others think of you doesn't stop you from getting very comfortable in all sorts of situations.
You might also want to find ways to give yourself a crash course in frame control. I surrounded myself with aggressive, insensitive people as friends and girlfriends, and spent years going out to nightlife, to rid myself of as much of that stuff as possible. I was pretty awkward/uncomfortable at first, and even pretty awkward/uncomfortable after a year of it (sometimes wondering how I managed to get cool friends and sexy girls in bed and as girlfriends when my awkwardness seemed so painfully obvious to me... I chalked it up to "Well, I guess them being insensitive means they aren't as sensitive to my discomfort, either"). But after a few years of putting myself out there into every imaginable social situation, as often as I could, I realized one day I was obviously more chill and in-control in most situations than most of the people I met. And then it just kept going from there.
You can do it. It takes a lot of exposure. But with time and exposure, you'll get there.