From the Createx website...
Createx Airbrush Colors and Wicked Colors cure best when paint is thoroughly dried prior to application of heat.
Do not heat cure fresh paint before it air cures for a few minutes. Premature application of heat may skin-over paint creating a latex film which peels easily when taped and otherwise lacks proper adhesion.
Createx Airbrush Colors are not cured after drying, heat is required. Wicked Colors air dry to a durable film without heat curing although use of heat does achieve optimum film strength.
Heat Gun: apply heat at a low to mid-temperature setting no more than 300°F. Keep air moving to avoid blistering. Apply heat until paint is warm to the touch.
Shirt Press: 325°F for 15 –20 seconds.
Iron: With a protective cloth over paint, set on high/ cotton setting and iron for @ 2 minutes. A shirt press or iron is recommended for curing t-shirt artwork intended for washing.
It says the heat gun should not be above 300 deg F, not that you need to heat the paint that high. Paint should be heated "warm to the touch" to heat cure. I think a hair dryer will do that job. The hair dryer I use reaches 185 deg F. That's actually VERY warm to the touch! They recommend letting the paint dry for a few minutes before "heat curing". Should be no harm in using lower temp air to speed up drying.