I have seen some beautiful outcomes from this technique, however I have also seen some serious fails! Hence why I have never attempted it before!
It took a long time and lots of trial and error but I eventually got a half reasonable result!
In case you're interested, here's the story of my disaster:
I didn't have any spray alcohol gel, so after watching a few YouTube video's I started off trying to use hairspray. Massive mistake. The hairspray just seemed to instantly dry the polish and make it sink to the bottom. So I tried again. But there was hairspray residue left on my water, which the polish sat on top of. I took my toothpick and tried to remove the layer of hairspray, but it seemed to be never ending. Each time I took some out, more filled the gap!
I emptied the water out to get rid of the hairspray and started again. But somehow, there was still hairspray on the water! Several cups of water and many toothpicks later it appeared hairspray-free.
So, if hairspray doesn't work, how am I going to do this?
*Trawls Google for another hour*
I dropped my polish onto the water, it dried instantly and sunk to the bottom in a ball because my water was too cold having come straight from the tap. Doh.
After microwaving my water, I again dropped my polish onto the water, let it spread, dipped a brush in acetone, flicked it at the polish andd... nothing happened? The acetone seemed to evaporate in the second it took to move the brush from the bottle, to the polish. So I tried again. This time I held the acetone over the polish, so it dripped in as soon as I took the brush out. I ended up with a massive clear circle in the centre of a tiny ring of blue. Third time lucky? I dipped into the acetone, which was as close to the glass of water as I could possibly get and gently tapped the brush over the polish, creating little 'holes'. Success! At last!
Conclusion: Biggest hassle ever! Safe to say I never intend on water spotting again!!