Outside of any training you receive from the equipment manufacturer/distributor, trial and error is the key to success in D2 printing. If you have never used this type of equipment, buy blank garments and expect to throw them in the junk pile afterward. There are a couple of things to keep in mind to make the D2 process run a little smoother.
The shirt style itself can affect the print quality. For example, an extremely soft, ring-spun cotton white garment typically absorbs the ink more than a standard cotton shirt, making the print less vibrant, whereas a ring-spun cotton dark garment is often the best shirt to print on. Taking notes throughout the process will help you better understand the variables and help you to retain the information moving forward.
Refrain from using white ink in your system until you have mastered the use of your software and maintenance of your equipment. The problem isn’t so much the white ink as it is the pretreating process or preparing your garment to accept the white ink. The amount of needed pretreatment varies depending on the garment style. Ring-spun cotton tends to need much less pretreat, giving you a softer feel, whereas a standard cotton shirt most often requires more, which results in a heavier feel or hand. There are also blends and tri-blends in which some work better than others and some not at all. This is part of the learning experience and mastering the basics before tackling the white ink process allows you to absorb the information and not become overwhelmed.
Most people are excited to receive their equipment and begin selling, but it is best to not take on any paid work without understanding some of these basic principles. D2 printing is repeatable once you master the basics, but if you don’t allow for the additional time needed throughout this process, it will be much easier for you to let the equipment sit than utilize it for its intended purpose.