There won't be a glue line if you scarf. I pre cut a 7 to 1 scarf on the end of a lot of my strips before I start stripping and glue up any longer lengths I need in advance. I cut 5 scarfs at once on my radial arm saw placing the strips edge-wise in an angle jig. You can also do that with a miter saw too.

Then I use a jig which makes it real easy to glue them up. Spring clamps on the ends prevent the joint from sliding apart

http://www.outer-island.com//photos/scarf-jig.jpg

It takes me about a minute to glue one up - I use them the next day. I place a scrap of strip with tape on it under and over the joint so I don't dent it with spring clamp. I take it carefully off the jig and slide the jig forward to do the next one. I do this on the floor. You have to be careful that the joined strips don't move out of perfect parallel alignment.