the easiest way is to set blender up in a way that you only need to press one button, i do it that way for 4 month now after i got the tip how to better my workflow and it save a hell lot of time
this is the way i do it and it always works for me:
i have simple folder on my HDD where i store all my mod source files for easy editing (called 0_my_mods, 0_ is only there so the folder shows up as the first entry) inside this folder i have a folder called "base"
the base folder needs following files inside it
you get all of this if you extract the def.scs once and copy the needed files into the "base" folder, the unit/hookup folder is in the base.scs, also needed or you need to assign every locator for lights/particles again (bet for prefabs this is also true)
also, copy the conversion tools into said mods folder also for easy finding
if this is set up i import a model into the base folder from the game (wich ever you want here i have the cabs from the Renault Trucks T), if the import is done, change the SCS Project Base Path to the folder for your mod (in my case Renage_T_Rework)
set the path for the Coversion Tools also
if this is done, scroll down in the Scene tab
until you see the Export Panel
there you set where the model should be exported to if you are done with your edits (in my case //vehicle/truck/renault_t), the moment you hit Export blender will export the files into your set location
now the Conversion Helper, here you set the path where your mod should be exported to completely ready for the game, be it in a separate folder (like i did it) or directly into the mod folder of ETS/ATS, this is up to you how you want to handle it, below that you set the name for said mod (self explanatory)
then you have some options, i let them be as blender has them by default, only i changed "deflated" to "no archive" this way the mod will be exported as a folder and you can do easy editing in regards to def files without unpacking the mod every time
now if you hit >>>>PACK MOD<<<< blender will convert everything inside your mod folder (in my example everything inside Range_T_Rework) to a game ready mod to your chosen location in wich ever form you want it (as a folder or .ziped archive)
you complete mod can be saved inside the SCS Project Base Path, all defs, all ui related stuff etc. for me it looks like this (Range_T_Rework mod example, the number of folders can vary if you change more stuff like models, flares, prefabs etc.)
blend_source > here i have every edited model saved as a .blend file for easy access to them (wont be converted by the conversion tools)
def > every def file i changed or need for changed/added stuff
material > if you have custom ui icons fr your mod there go here
vehicle > every model file you changed/every custom texture you added that isnt present in the game base files
manifest and preview image for your mod, not needed but better to keep it clean
i hope this is somewhat helpful and complete, if something isnt clear to you ask and i try to help understand it better if i can
