I have only recently started using top/overcoat on my nails. I never saw the necessity in it before. But topcoat really is important in doing your nails. Painting nails, overall, is bad. The horrid smell definitely is not healthy, and I don't think paint going over your nails layer after layer is good either. Then, once your nail color chips or you get bored of it, removing it with nail polish remover isn't a plus to your health. I'm pretty sure the stench is even worse than that of nail polish.
However, using topcoat will make your polish last almost twice as long without chipping, therefore, making painting your nails less harmful to you!
But THIS top coat is terrible. BAD BAD BAD. I don't know why, but even when my nail polish is completely dried, when I apply this topcoat, it makes my polish UNdry, and ruins it. I hate it whenever I spend a long time making my nails perfectly smooth and shiny, and then I accidentally touch them, and there's a big smudge on my nail. Well, this topcoat does that. It smudges the color and creates a lump of uneven polish on my nail. IT SUCKS. Don't buy this.
PS. Like the picture I took of it? That is the product of a GOOD CANON camera. My stupid Casio Exilim one doesn't even have a macro function. Well, not one that I can find at least. >;(
Haven't made a nail tutorial in over a year, if I recall correctly. I only did my right hand, and I will film myself doing the left hand tomorrow, when the lighting is not so non-existent. Here's a pic though:
