Screen printing wet on wet can save a lot of time. But to be able to screen print wet on wet there is a couple things that should be considered, and that is the correct color order to print or what screens need to be printed first, second & third. The most common color order for screen printing on light and white T-shirts is to print light colors first then darks. For printing black and dark shirts the color order is reversed. Start by printing an under base (if needed), then flash the under base, and then print dark colors such as blue, purple, brown, followed by green, red, orange and then yellow and then lastly the highlight white.
If none of the colors are overlapping you may be able to print wet on wet. However this is not always the case. When printing wet on wet the inks are often picked up on the backs of other screens printed later in the color order. This can reduce the brightness of the ink color as you move from one screen to the next. Therefore you may need to print a couple colors wet on wet then flash and then print the remaining colors wet on wet. Another need to consider when printing wet on wet is the amount of design in each screen to be printed; if a screen has a small percentage of design to be printed it should be in the beginning of the print order. If a screen has a large portion of the design it should be one of the last screens to be printed. This way you can print wet on wet and the large design will not have a lot of ink build up on the backs of other screens/colors to be printed after it in the color order.