Yeh I 've seen a lot of Eindecker cowls with the swirls done in a regular pattern and that is not how the real aircraft appeared. The swirll effect was very random and that is almost harder to do than a regular pattern. I simply sanded the cowl and sides with a 400 grit wet n dry and than I used the steel brush tool from the dremel tool on a slow speed.
If you want the plane to look just a little better you can also put some fairings on the landing gear and pylon. If you use bass or hardwood it will also strenghten the gear. I used basswood and made a groove to accept the wire. I epoxied them to the gear and then wrapped them with some of SR's metal tape.