Thanks, John. As I mentioned, a freehand application of RLM 76 was what I intended next. As it happened that went pretty well. I ended up going back and forth between the 74, 75 and 76 in one session. That was going even better until I did something truly stupid and against my best instincts. I decided to use a lightly held paper mask to touch up the splinter between the 74 and 75 on the spine. Alarm bells went off in my head to wait until the 75 was dry before pressing down on it. So much for hesitations. I went ahead and, of course, the mask stuck to the tacky 75 on the spine and left behind significant residue.

ARGGGHH! I have an approach in mind to fix it but I have to wait at least two days for it to cure first. When it is hard, I will try to polish it out. I am hoping the paper fibers only stuck to the outermost layer of paint, since I painted the spine first yesterday. If so, I might be able to smooth it out without digging down to the plastic. If I go down too far to clean it up, I will have to strip off all of the paint on at least the two segments affected and start all over again. Too bad, I was really pleased with the mottle otherwise. This is the point where you either go nuts and trash the model or take this as the ultimate exercise in meditative calm and learn patience from the hobby.

Thanks, Spiros. Your confidence and kind words have cheered me up considerably. As the paint cures, I am even more satisfied with the mottle. If I can rescue the finish from this mishap it will have been worth the wait and the effort. It's funny how much bigger a blemish looks when you are staring at in high magnification for a while. I will handle this one way or another.

Do NOT trash this 109, Colin @coling
I fully understand the disappointment when it happened, but like you said, there are ways to get this repaired in a good way.
With your modelling skills you will definitely get it done nicely.

Hey Pedro @coling, I know how frustrated you must feel about this, but I'm sure it will polish out quite easily, patience is a virtue...

Thanks, Jorge (George) ha ha. I guess my last name does suggest "Pedro" rather than the rather Anglo-Saxon Colin. Anyway, I appreciate your kind comments. Patience does indeed pay off in this case.

I finally fixed the blemish and also enhanced the accuracy of the camo a bit in the process. Following Bill Koppos' excellent advice, I easily removed the paper fibers with a moistened finger tip. I elected to follow this up by carefully polishing the affected area using a three part nail buffer. This helped to eliminate a bit of residual unevenness in the paint. I then resprayed the RLM 75 to further smooth things over. I am very happy with the results, which pretty much erased my error. After studying the Eagle Cals sheet photo of 3 JG 53 109s, I decided to respray the RLM 76 areas again, adding a drop of flat white to heighten the contrast with the 74/75. I am happy with the softness of the demarcation line and the very subtle mottles - almost non-existent below the canopy.

The darkest area is clearly the cowling in all pics of real JG 53 aircraft and I think I have captured this pretty well. The three pics of Hammer's bird that I have (taken earlier in Italy) are not so clear in mottle details but later JG-53 aircraft share a lot in terms of how the camo is done. I will be doing quite a bit of weathering later on, such as heavy exhaust staining and darkening of the panel lines with oil wash technique with post shading, so I am good with leaving this stage as done. Next up will be to let the fuselage color cure before masking and doing the wings and tail. I hope this looks good to you. Happy modeling.