Nope... It's fast if you use Blendup.
Just Hide all edges and then, unhide where you want your seams to be.
Then UNwrap there using the Unwrap tool. It should be a straight forward job to you (because it is for me).
The only thing is that when your model comes back to sketchup, if modify it's geometry without a plugin that keeps UV maps (like SubD or Artisan do) you are probably f''' up and need to redo the map... But then again, with those seams in the right places it's fast.
For flat faces it will be better to UNwrap in Sketchup.