What is the best way to estimate materials accurately for handyman and remodeling jobs?

I run a Handyman/ small remodeling company and one thing that always seems to slow me up is material lists.  For some of the bigger jobs we do such as decks, its not too bad.  I typically get on Menards and use their design and build tool which gives a materials list for the project.  This usually gets me about 90% of the way there, typically will have some additional things here and there.  Where I typically get hung up is the more odd jobs.  I spend time thinking about all the possible things we will need and it seems like always fall a little short.  

My question is what are others doing?  Same thing?  AI tools?  Just getting materials close enough then billing out extra at the end?

appreciate any and all help!