Submerge the toothbrush with the tongs.
The water really needs to be boiling. The tongs will keep your hands safe and unburned.
Towel in hand, remove the brush with the tongs and bend it into shape.
Don't forget to use the towel! Otherwise you might get burned. The brush will be flexible before it cools down.
If it stiffens too soon simply submerge the toothbrush again and repeat the process.
Skip this step if you managed to get the shape you like on the first try.
Try bending and twisting!
You can get all sorts of unique designs if you play around a bit. Twists are simple to apply. Try adding kinks and turns to add uniqueness.
And there you have it.
Toothbrushes aren't exactly expensive, so try experimenting and enjoy.