My recommendation for most people building three or fewer packages is to set up enough configuration to run bloom, then create your own environment for actually building the package. If you're building many packages it might make more sense to create a ros_buildfarm_config repo so you can take advantage of the automation.

It's possible to use the ros_buildfarm library to create binaries for your package without setting up a buildfarm deployment. However it does require that you set up most of the configuration for a buildfarm deployment and you need to provide a local rosdistro cache. I've built mock buildfarms for this purpose before but it's very involved and it's not something I've been able to package in a friendly, redistributable way.

Generating debian metadata with bloom requires creating less configuration. If I recall correctly, just a custom rosdistro index and distribution.yaml and possibly some additional custom rosdep keys. Once you have the debian metadata created you can build the debian package in any environment you want. The ros_buildfarm scripts only automate the process of creating an isolated container, installing dependencies, and running the package build commands but to automate all that requires more configuration as outlined in the previous paragraph.