Mask fogging up?

Some of you may have issues with your mask fogging up. This is usually due to some sort of greasy residue on the inside of the glass (I'm supposing you have tempered glass). If the mask is new this is often caused by the manufacturing process; if it is not new this is often due to you touching the inside of the glass with a greasy finger (e.g. with sunscreen, body oil, sweat). A foggy mask can ruin a dive. I have tried using spit, this worked ok but not as well as I expected. I tried special sprays, this didn't work as expected. I found this tip and have used it successfully ever since, after a dive:

1. Rinse the mask well with fresh water; this removes the salt.
2. Clean the inside with liquid dish detergent (the kind used hand wash dishes); this removes the grease. You can skip this step if you don't have any, it should be ok.
3. Once dry, spread (using clean fingers) toothpaste on the inside glass and let it dry; this cleans any hard to remove residue without scratching the glass and protects it while in storage.
4. When you want to use it just submerge it in water and shake it around; the toothpaste will go away (it may take a minute or two).
5. Do not ever touch it with greasy fingers!

I hope this helps someone.