This is how I create semi-realistic flame effects in Photoshop.
Small Candle Flame
Step 1
Using the paintbrush tool on a new layer, create a small, vertical, soft-edged blob of red-orange with a smaller blob of orange and an even smaller blob of yellow inside it.
Step 2
Using the smudge tool with a brush size slightly larger than your blob, smudge the blob upward in a wavy motion.
Large Flame
Step 1
Using the paintbrush tool on a new layer, create a large, horizontal, soft-edged blob of red-orange with a smaller blob of orange and multiple small yellow blobs inside it.
Step 2
Using the smudge tool with a large brush size, smudge the blob upward in a series of wavy motions.
Step 3
Smudge the bottom of the blob downward to create an uneven base. Continue smudging the middle and top of the blob upward.
Step 4
Using a smaller brush size (about half the size you used in steps 2 and 3 or smaller) refine the shape of the flame with small, arching and wavy strokes.
