I humbly suggest another method - especially if you are fairly new. Leave the panel lines alone. When you are finished painting your eagle, then use the drybrushing method to pick the raised panel lines out.
Simply put, mix some of the base color you used to paint the eagle in, then darken it by 20 -25%. Dip a wide brush in the mixture and then wipe it on a paper towel or napkin until there is no more paint coming off of your brush. Now gently scrub the surface of your model until the panel lines slowly start to appear, highlighted by the darker color on the brush. If you have done it correctly, the panel lines will appear, and they won't look too stark.
BE PATIENT, go slow and you may want to practice on some parts or other models before you put paint on your airplane.
A second method if you are using an airbrush is to take a darker mixture such as I have described above and paint along the panel lines with the darker paint, and then go back with the original color and blend it in until only a subtle line remains.
Scribing panel lines is one of the single hardest tasks in modeling, and I DO NOT recommend it unless you are committed to the look. There are a lot of great F-15 kits out there with nice recessed panel lines for not very much money, and that is a much better option (getting another kit) than spending weeks rescribing a kit that really isn't worthy of that much effort. Hasegawa and Academy both make 1/48 Eagles that are really nice, and if you have some $$$$, try and get the Tamiya 1/32 F-15C. The kit is museum quality.
Best of luck to you. HTH.
Scott