The key to tamiya acrylics is the grade of alcohol used, isopropyl alcohol (also called Isopropanol or rubbing alcohol) comes from the pharmacy in various grades anywhere from 50% to 95% alcohol, the rest being water. I recommend the 90+% as the excess water can be an issue. Water evaporates slower than the alcohol, so when the paint film is drying and the alcohol evaporates you end up with pigment, resin and water. Since the resin is not compatible with the water without the alcohol you get water and resin domains (think how oil and water do not mix, and drops of water in oil) which provide poor quality, since in some areas you only have pigment and water without resin holding the system together. The alcohol evaporation rate is based on the temperature, while water evaporation rate is based on temperature and humidity. This issue of water remaining in the film during film formation is worse if you are painting when the humidity is higher. I also recommend you use the minimum alcohol possible, as excess solvent can lead to other coatings issues. If you are spraying and add alcohol, adjust the air to paint ratio for the best atomization to evaporate most of the solvent before it hits the part. One day I should make a video on painting and paint technology.