I tried with three or four times before binning the product with applications still to go. The mixing etc. is fine but having to smear around your eyelashes with vaseline and not touch the eyelashes is ridiculously tricky.
The chemicals did make my eyes water.
This did darken the colour of my lashes and I feel if you have naturally thick/long lashes this would be excellent but I have sparse, fine lashes so just darkening them didn't do too much. For me the faff didn't deliver good enough results to keep going.
You need to leave it on for the maximum time to achieve a noticable difference.