Best Practice for custom repository

Good day!

Where I can find best practice for work custom repositry for linux ?

Example: remi, nginx, adoptopenjdk dont have an official support of bigfix and dont have a fixlets for update it.
So, how we can update this packages ? What Best Practice or Suggesting for it ?
We should create fixlets manually for each package ?

All hosts have access to it repository directly.

We Use a fixlet running yum Update.