I am posting a simple tutorial for hand brushing Tamiya acrylic paints. Let me start by saying that Tamiya paints will appear darker, when not airbrushed; and, are sometimes a different color entirely. That being stated, here are some simple steps for hand brushing Tamiya’s acrylic line:
What you will need: Tamiya Acrylic Paint and Primer
Isopropyl Alcohol
Paint Brush
A small cup
A rag or piece of paper towel
1)Clean and prime the piece you will be working on.

2)Mix your paint either by shaking or stirring, I prefer shaking as
there is less mess and I don’t loose paint on the agitator.

3)Pour a small amount of IPA into your cup.

4)Dip your brush into the cup of IPA.

5)Drag along the rim of the cup to remove some of the alcohol.

6)Load your brush with paint.

7)As you run out of paint on your brush rinse in alcohol as
prescribed above and, drag the new paint towards the previous
stroke.
This keeps you from rubbing the dried paint off of the model.

8)When painting lighter colors, I recommend base coating the are
to be painted with white.
Generally, you will need to apply two coats of white before
painting the top coat.

9)Every few minutes remix the paint, as this helps to keep it from
drying out.

10)To dry brush, follow the instructions above.
However, mix the topcoat with white approximately 10:1.

11)Paint fine lines on the raised areas and let dry for a couple of
seconds.

12)Rub your thumb across the raised areas to cause the paint to
smear.

13)To effectively add shading, simply mix the paint used for the top
coat with black approximately 10:1.

14)Dry brush the recessed areas by dragging your brush across
your paper towel or rag after you have loaded it with paint.

15)Clean your brush every five to six minutes to reduce paint build
up.

16)Rinse your brush out with alcohol and gently drag across the
rag you are using.
Hope this helps some of you guys.

IPA is a drying agent, and I would suggest NOT using it for brush painting. A drying retarder would be better. I've had luck using Tamiya thinner, as it does slow the skinning effect, and drys slower than IPA will.

Be that as it may, IPA actually helps to keep the paint from skinning. There is no reason fo purchase Tamiya thinner. You don't want to add a second coat to paint that is still wet. This will cause it to roll off of the plastic. Use IPA to provide a uniform and smooth coat of paint. I've just finished 20 figures, painted with Tamiya acrylics eclusively.

Matt,I do not have any primer and no eay way to get any.Can I use a flat enamel to prime with I'm using mm and testors,it seems to bite to the plastic well,and with the flat finish the tamiya acrylics I have ordered should stick well Thanks,Jeff

Actually if you use enamel paints you don't need any primers.
You'll have just to clean your model very careful and spray your base coat
If you have to paint the details with an acrylic paints you can apply a light gray coat of enamel before. After a right drying time (at least 2 or 3 days) you'll obtain a perfect and sturdy base for acrylic colors. Furthermore, acrilic thinners don't damage enamels paints, so if you make some mistake you'll be able to wash them away

I forgot to put a question mark at the end of my text.Any way Mauro thanks for the info,I have 4 figures to do so I will try it both ways Jeff.......Matt thank you also for the step by step will be following it when I get ready to start.

Thanks for this Matt, I tried some of the techniques out on some of test figures today!

Out of curiosity, when shading flesh, does the same 10:1 principle apply?