I am INTx and consider myself as what I think is called "social introvert".
My preference for introversion is clear but that doesn't prevent me from being sociable. I like getting to know new people, I know how to deal with and get to know all sorts of people etc. Often, it really drains me, and therefore, practicing those skills is not too easy for me, but I have found it very useful a skill and thus, I do practice it.
I think INTx consider sociability and becoming sociable quite differently from other, especially from extroverts. At least I think I do. My need for interaction with people just for the sake interacting with people is quite. Some of my hobbies, however, are such that even though I can do and enjoy them alone, I can clearly see that sociability is a great advantage for me with them. It is very good to be able to generally deal with people and to be perceived as someone who deals with people not just for personal interests but to really connect with them.
I have read that INTJ have better pattern recognition skills than any other type does and I think that might hold a truth. I am not someone who just runs into any situation and learns by doing (as I assume extroverts learn their social skills) but I rather observe other people dealing with each other. I see patterns of interaction between people in different situations and I see what works and when. I draw conclusions regarding how to act in those situations and eventually, when faced by chance, I test my conclusions. Sometimes they do fine, sometimes there is room for improvement. I analyze my actions and the outcome and let my intuition subconsciously figure out how to improve. It's slow but for me it really works. The more I practice, the better and more accurate my intuition gets improvising in different situations. So far, I have advanced enough to stay motivated.