One of the important steps and tools to achieve defined eyebrows are :
After doing your eyebrow measures and had imagined a good shape for your eyebrows, you will need to draw it, trace it very precise fine smooth line, with out being blurry and messy.
To achive that definition in the eyebrow's tracing is important to have the best brush , that means it has to be a good quality angled firm thin synthetic brush
I could recommend so far this 3 ones which have worked perfectly on me and clients
1 - space NK liner brush
2- benefit's angled brush for eyebrows /liner
3 Mac's angled brush# 263