Best practice for preloaders

Dear all,

I want to start dealing with preloaders for my project. I do not have enough knowledge to do it without asking. So I hope you can advice me.

This is the situation:

  1. I have to load a XML file which is around 190K. I am using URLRequest, URLLoader and Event.COMPLETE
  2. Now I have around 50 small movie clips in the library which I load dynamically using addChild. According to some articles is better to load the resources from external folders, this is for security reasons. So I am considering to load them in that way but this means I have to load 50 movie clips. I do not know if it is possible load a folder at once.

I will appreciate the help you can give me. Advices and recommendations will be welcome.

Regards.