Skinny--I wouild presume that when I do change the fuel filter, I must fil it with diesel fuel first?
If you have a primary and secondary you would only fill the primary. If you only have one spin on then no.
The theory is that when you fill by hand any contamination in the fuel is bypassing the element and going into the injection pump.
Sure there is variation depending on if the filter is a standard vs. reverse flow ie. which way does the fuel go in the filter.
But a better habit would be to figure out how to prime the filter and pump without filling the filter. Whether that is compressed air going into the filler neck or putting a hand primer on the filter head.
I'm sure it would be fine but it's probably a bad habit with a diesel filter since we are taking microns here.
What do you have for a filter?