Looking forward to see the rudder painted, my friend @gblair!

That was some serious puttying - looking good!

Ever have one of those days? It was supposed to be an easy day with just adding the light blue color on the bottom of the plane. First I decided to add a bunch of the small bits that I had left off till now. I also rigged the support wires on the horizontal tail surfaces. So far, so good.

As I prepared to paint, I made a series of poor decisions. I decided to paint the red stripes first, as they would be easier to mask later. I painted a layer of white first, but it went on a little thicker than I wanted.

So, I sanded the white with some fine sandpaper to smooth it out. I ended up with some of the plastic showing beneath the white. I thought it might work a pre-shade, so I left it like that. (Mistake 1)

I had used Vallejo ModelAir Ferrari Red for my previous build, and thought it would look really cool. (Mistake 2) It turns out that the red was very translucent and allowed the sanded areas of the white to show through quite clearly.

I added some yellow to cut the translucency, and then sprayed a random pattern on the red. A little better, but I added some white to the mix and sprayed some more random patterns. A little better, but you could still clearly see the plastic showing through the red. I did a quick clean of the airbrush and decided to spray some Tamiya Flat Red to cover the problem areas. (Mistake 3) The Tamiya reacted with the leftovers of the Vallejo and created tiny clumps of coagulated goo. I managed to get the Tamiya Red sprayed and got a sort-of OK looking red that will serve as the stripes.

Next problem was cleaning my airbrush. Several cleanings with Tamiya X20 followed by 90% alcohol still left vestiges of the red mess that I couldn't quite get out.

My wife gave me a really nice tool for my birthday several months ago that saved the day: a sonic cleaner. 180 seconds in the sonic cleaner and everything was clean and shiny. Yeah.

I may still end up repainting the stripes, but I want to see how they look after I apply the camo colors. Time to go relax and plan the next paint session. Cheers.

2 additional images. Click to enlarge.

A far from relaxing time at the bench, George @gblair
It seems like you got it done now.
The tri-color rudder does look excellent.
Ultrasonic cleaners are very practicle, luckily I can use them at work if needed.
I also see that you use those Gum dental sticks, from personal experience I can say that they are very practicle for cleaning an airbrush as well.

Thanks, Spiros (@fiveten), John (@johnb), and Erik (@airbum). Two of those tools that I didn't know I needed until I got them are my sonic cleaner and dental brushes. Very useful. My granddaughter is coming over today, so I don't know how much hobby time there will be. I hope to at least get the azure blue on the bottom of the plane. Enjoy your weekend everyone.

A better day it was and a superb result so far, my friend @gblair! Your fading technique is second to none!

Advice for the next time you have this paint problem happen (and the only question is when, not if; we all do it more freuqently than most will confess): when it goes "pear shaped" like that as our Brit cousins say, take some "409" cleaner and spray the paint, then rub it off down to bare plastic (409 is a great acrylic paint remover, it won't harm the plastic at all). Start over and do it right. As you have seen, trying to mitigate a problem only creates a disaster downstream.

How much is one of those sonic cleasers?

This plane only has one marking, a serial number on each fuselage side over the red band. There are no pre-made decals for this plane. I was tempted to use some decals from an I-16, whose ID number was the correct size and font, but the D.XXI had an ID number that started with "CF" and the I-16 had a registration that started with "CM". I resisted the temptation to use I-16 decals even though they were quite right. I found a font that looked correct and made some decals on my printer that would work. I got some fairly thin masking vinyl that I wanted to try but was concerned that the markings might be too small to cut on my wife's die cut machine. The thin masks cut perfectly in her machine and worked great with no bleed. The only problem that I had was that the masks were so sticky I had trouble removing them from the plane. I managed to nick the red paint with my Exacto when I was trying to lift the masks, but that should be easy to fix. My last task of the day was to mask and paint the radiator ring on the front of the cowling. I used a really old bottle of Model Master Burnt Iron Non-Buffing Metalizer, but it worked great even though it may be 30 years old. I hope to get some weathering done tomorrow, followed by final assembly of the small parts. Finally in the home stretch.

5 attached images. Click to enlarge.