He might have everything he needs for a WA. state title on a trailer already. Kind of impossible to know w/o asking someone at the WA. DMV or licensing shop, WA. has these unique shops everywhere where you can conduct DMV business.
I've belonged to AAA forever and do most DMV transactions there but sometimes you need to go to a real DMV. It's a myth that going to the DMV in CA. is always a nightmare-I just renewed my DL @ DMV in person last week and it was a breeze w no appt. I brought a good book expecting a 2 hour sit and it was more like 10 minutes.
It takes a long time to get an appt. @ CA. DMV in Los Angeles, I just went to the easiest one according to a google search and it was a piece of cake. I can't say which one because I don't want to promote it but it was also 10 minutes from work.