Let me try and explain: imagine that you went to work by bus every day and then you bought a car and now you travel by car. You would then say:
I used to travel to work by bus but now I have a car and I travel by car. What you are describing is something you did regularly every day in the past ‘used to travel by bus’ but now you do not travel this way.
When you want to describe something that you do/did/will do (it can refer to any time/tense) and you want to say that it is something that is not a problem for you because you have done it so many times then you use the construction ‘used to’ + ing or ‘get used to’ + ing.
For example I have been teaching English for many years and so it is not a problem for me (at least I hope so!) to explain a point of grammar. Imagine this conversation:
Claudia: Can I ask you a question?
Me: Of course you can
Claudia: I hope you don’t mind
Me: Don’t worry. I am used to answering questions.
Your other point about ‘their’ is one of my favourites and I’m pleased to say it is slowly changing. You can say: Everydody is following his/her interests. Personally I think this sounds horrible and I prefer: Everybody is following their own interests. Similarly: A child must be allowed to express their personal opinion about life. So I believe you have a choice in what you say/write but I prefer they/their. Everyone must make THEIR own choice.
Alan, you mustn’t hope. I think you don’t have a problem to explain things like grammer to other people. I like your explainations and I understand them most of the time. The time I don’t understand them are my problem I think, because my English isn’t good enough sometimes.