Hey, George,
Lovely work there. As for filling some of those "weird" to sand things.... I rarely ever sand anymore. Put tape close to either side of the gap (when possible), smear in some Tamiya white putty with a toothpick to minimize overflow. I then grab a Q-tip, dip it some acetone and wipe the putty away with that. After the putty is set, I wash the area with warm water and some Dawn dish soap to get any remaining acetone off the plastic. I have never had any damage on the plastic and the seam / gap is very nicely filled with no sanding required. I used this on the P-40 I am doing for this build. The landing gear "end caps" had some fit issues. After looking thing over and thinking about how to sand that compound curve against that soft Airfix plastic, I went with the putty / Q-tip / acetone thing and it worked great. No sanding needed at all.
I do like the Eduard 109s, especially the Gs. The 3 I have done have all been great kits with minimal fit issues. If I used more than a couple of drops of putty I would be surprised. I love the subject you are doing as well. I was trying to find some Italian markings for a 109 E7 and no bueno. I was thinking about an Italian plane with a 109 E7 I started while waiting for my PE for the P-40 for a possible addition to this GB, but no luck on finding anything yet.
Oh! Thanks for the tip on the wax pencil! I just ordered a box of 6 off Amazon. These will sure make getting those small things in place a whole lot easier!