USB will be limited by the speed of USB2 in the 2008. Wifi is also slow as hell and often fails. Couple of easy options:
Ensure both machines are fully updated:
- connect both macs via ethernet (wifi is too slow) and run migration assistant
or
- put the 2008 in target disk mode and run migration assistant
or
depending on if the '08 is running a new enough OS, put the '13 in target disk mode, and clone the '08's drive to it. This is definitely a quick & dirty to get up & running. I would keep a fresh OS on the '13 and find a way to run migration assistant. Or just copy your home folder over.
[edit] ack, after all that I just realized that OP only wanted to transfer a few things over...