Yes, you can use a regular hand held hair blow dryer for drying your watercolor paintings. The key is not use the blow dryer until the watercolor paint and water have finished doing their job of mixing, mingling and blending. You can speed the drying process by using a blow dryer on your wet watercolors. Make sure the watercolor paint is not drippy wet, otherwise you will run the risk of blowing the color across the page to areas where you don't want it to be.
Blow drying your watercolor paintings can speed the drying process so you can go onto the next step. You definitely want your watercolor to be completely dry if your next step involves a hard edge or a fine line.