For the first time out looks good to me. Those older Tamiya kits are perfect for testing new techniques. Excellent choice!.
With that said I don’t use pre-shading.
Please feel free to ignore everything that follows below.
To me Pre-Shading involves guess work since the contrast and shading intensity are basically set before the color is applied. When one’s familiar with the colors and paint involved much of the guess work goes away I’m sure.
With that said, I’ve seen quite a few excellent modelers end up unhappy with Pre-Shading results and end up stripping paint for a redo.
I favor an old school technique called Shadow Painting. Its more of a linear dark to light what you see is what you get technique. Its usually a little more labor intensive but gives excellent results.
With SP, an off black or dark grey is applied to the entire model first. Next base color coat is lightly applied leaving shade in recesses. Off white is added to the base color lightening the base color and that’s applied to the larger open areas. Last, more off white is added to the prior lighten color and the largest areas are lightly covered. The base of black plus three thin coats create lot of tonal variety. This technique is easy to learn because one builds the color from dark to light and can adjust at each stage. If the color seems a bit light, randomly drybrushing of the base color on to open surfaces helps correct.
Example of Shadow Painted model.