Q.Cutting/triming down an Avocado tree
This project has to be self-help I am able to get to the top of the tree. Is there a way I can start at the top? Bottom? Start trimming, cut the top off? How far down? Completely cut limbs off or trim them back? Have the tools and help. My most important question is just not cutting the tree down the end! but a way I can reduce it down in size. Avocado tree 18′ ft high very healthy

Certified GKH Gardening Expert
I can point you to sources that can help, but I do not recommend taking on such tasks without professional tree service guidance.
Here are some sources that can help:
https://www.pubs.ext.vt.edu/430/430-458/430-458.html
https://extension.umaine.edu/fruit/growing-fruit-trees-in-maine/pruning/
https://ucanr.edu/sites/Tuolumne_County_Master_Gardeners/files/160549.pdf