The best way to avoid cracks and thick heavy t shirt transfers is by preparing the artwork before you even print your transfer.
Rasterization is the process of adding breaks to the transfer to allow it to breath, increase stretchability and softness, and limit cracking and wrinkling which can happen when transfer has large solid areas of ink.
Rasterization is particularly important with certain types of heat transfers like White Toner and even direct to film. But how do you do this while keeping the artwork looking good at the same time?