I used to do it too and it turned great!
I also used Jolen. Just be careful to re-spread the mix after applying it because it usually starts to come off by itself.
Then check it every 2 minutes because when it reaches the colour you want you have to remove it right away.
I used to bleach them to have a softer brown and it looks great! It smooths your facial expression and if you have lighter hair than your own natural colour, it will harmonise more the "set".
It´s really easy! Don´t be scared!
