Toshi-san - Such a good job you're turning out on this one, looks really great. If you will be using the Neo for the final finish, if you have not already done so, I would recommend a look at Don Wheelers website, regarding the Neo. He did a thorough evaluation of that brush, and you can examine his detailed description of it.
You can also see how it's parts are assembled, along with his recommendations of the care needed to prevent damage, from cleaning or assembly mistakes. I had a Neo for a while, it will do a very good job for you. Best of luck with your continuing progress, I hope to see this project come along with photos of the paint job soon.
One last suggestion, if you have not heard yet, when using the Vallejo products be sure to not use alcohol, either for thinning or cleaning. Other acrylics work well with alcohol, Vallejo does not, it turns into a very gummy mess. Vallejo can be sprayed straight from the bottle, it also likes a little of their Vallejo thinner, but in my experience it takes VERY little of that thinner. If more than a couple of drops are added, it seems to require much more drying time which can be more than just a couple of days.
Usually I just give it 1 or 2 days to fully cure, when using more than a couple of drops of their thinner it has taken as long as a week. I have also used just distilled water for thinning, that worked well for me too.
Best of luck with it, thanks for posting.
Patrick