My mum brulees a lot of custard fruit tarts, using a little brulee torch, and for years she had problems getting that wonderful, brown crust. A chef finally let her in on the secret:
Melt sugar until it melts and browns in a pan. Then pour it onto a baking sheet lined with tinfoil. Let it harden, then break it into pieces, and blitz in your blender to the consistency of fine sugar. Sprinkle over your custard/tart, then brulee. It seems that after the melting of the sugar, it is much easier to break down and melt it again on top of a tart. Cuts her brulee time in half, and provides a better 'crunch'.
Don't do confectioners' sugar. It has a trace amount of cornstarch in it, and that won't melt, it will burn.
The best to use is turbinado sugar, also known as Sugar In The Raw. It gives the brulee an extra dimension of flavor, and gets a wonderful golden color.
Brown sugar will work in a pinch, but I'd go a bit on the easy side with it. The butterscotchy flavor could dominate the delicate flavor of the custard very easily.