Keep it simple.
3 x ht (ie 30,000ft = 90 miles)
Make an allowance for headwind/tailwind and engine anti-ice if
being used ( higher idle setting)
Use 'gates' on the way down. Approx 16000 at 50 miles - 10000 at 30 miles works for me.
Small corrections to profile made early prevent large deviations
in either direction.
Practice makes perfect
Good Luck