Yes, it is Gabreski's aircraft. I have still a lot of work with this one
I feel your pain with putty and sanding ... this part I really do not enjoy
I used to use Squadron white putty but ... I was told this stuff is not good ! And I agree, it is not a good putty to fill any seams like you shown.
For such cases use "Mr. White Putty" instead. It is much softer and a bit flexible, not so brittle as squadron white putty. This may be very important if you try to rescribe some of those filled panel lines.