I thin all Tamiya paints approximately 2:1 to 1:1 (Paint to Laquer Thinners) with an air pressure of about 15-18psi. You dont need to use Laquer Thinner, however, I find it will "dissolve" the paint better than ordinary thinners and dry much quicker.
The best way I find to check if the paint is ready is to AB, it that it should have the constiancy of skim milk when mixed together.
Try and spray a small amount of what every thinners your using through your AB (the same as you mix with the paint) before the paint to remove any residue from a previous spray session.