NO! You don't need a blow torch. Let me share a little secret...shuuuu don't tell. A blow torch will get the sugar caramelized but it will also heat up the custard. Custard always tastes best(in my opinion) when it is cold. I cook my sugar to caramel stage on the stove(sauce pot with sugar and water, cook till sugar is light brown) and then pour the sugar on the custard. This makes it so you still get the same nice crust but don't need a torch and you also don't heat up your perfectly set custard!
Hope this helps...