Short answer is no. Filler is pretty much only as much as needed, where needed, & as many times as needed, generally sanding off pretty much everything not needed. Determining all that is a combination of practice & planning & needs of the job/ vehicle condition.
Outside of any bad areas that you know need a skim coat of filler applied with a squeegee, running a long enough sanding block in a cross hatch pattern just enough to mark the surface of the epoxy basecoat will help determine how far to spread thicker filler by hand.
For a show car finish, some guys slather the entire car & block down right off the bat. The one advantage to this is also from panel to panel at the gaps trying to get a really flat even surface from one end to another. On the other hand this can be a lot of extra work. Personally for most jobs, I'd skim the worst spots & probably near gaps, blocksand that down as much as needed, then switch to a sprayable filler over the whole vehicle as needed/ if needed, block that down till it looks good . Then 2 k as a final spray & block.
Sprayable filler used properly can speed up the blocking process by not having to sand through the top uneven surface of hand applied filler just to get back to where you just where in the better areas.
Both hand applied & sprayable fillers can fill a fair amount of thickness, where 2k thickness shouldn't be abused.
There is a lot to this subject, but that's kind of a quick guide,,,,,, from one person's opinion & perspective of course.
