Cost Segregation algorithm

[Eric Lin]

Purchased a multifamily, would like to do Bonus Depreciation.

I am stuck at the  Cost Segregation

I see lots of people do 20-30% of house value(without land)

example: purchase price $100k, land $20k, other value $80k.

if we take 30%, would be $24k for Bonus Depreciation.

My question:

1. Can I do Cost Segregation like this by myself like this?

2. Do I need to hire professional for this? what is the most common way to handle Cost Segregation