Looking tidy, Nicholas....
Yes, it is difficult to get a straight line. Particularly, I remember, over the hull armoured belt.
Bit late for this, but for later projects of a similar nature, mark the lines with a pencil. I would think masking would be difficult for such a small scale. I don't mask anything, so I don't. know. Then paint the camo. in faintly to start with. Anything not quite right can be easily altered.
Then, when all looks good, give it a final coat.
You could still over paint anything you are not happy with. Just a pest that's all.
Just take your time finishing the painting, and all will be good.