Add "Mr. SURFACER 1000" to Tamiya's putty and knead it well.

It will soften.

Apply a soft putty to the parts surface with a hard and short brush.

You do not move the brush horizontally.
You must move it vertically.

And it is important that it does not become uniform.

When the putty has hardened, it is scraped with paper No. 400.
When you use this you need to do gently without adding power.

You must not scrape all the putty.
You scrape the surface a little and keep the bottom putty.

I use " GSI Creos' paint".
The reason is that when this paint dries, the paint film thickness becomes thin.

Because of that, it is possible to hold the irregularities of those surfaces.

I put a dark color there first, then put a bright color on the top of the surface.