If you start fresh (newbie) and don’t know that automatic BOM generation with order-list ready output might be desirable (doh) all your components will lack those fields (or once you finally make the switch from global to local libs all the former globals will miss those fields). The first thing I did was using KiCost as a BOM to XLS converter - so to speak - for a somewhat ordered central collection of those values.
I just copy&pasted the manf/manf# fields into the spreadsheet - doing this in excel is way more comfortable vs. doing this in KiCAD.
This naturally means KiCost couldn’t really do it’s main job - scraping those distributors - so all the order relevant fields where not populated 
If KiCost would had been able to take in it’s own output I could have had order-ready output after I had populated those fields in excel. So I had to manually copy&paste some areas of the spreadsheet and just went with DigiKey by using it’s BOM-upload facility and worked from there.
Another thing to consider for KiCost, is when you want to check some options for similar devices - adding a couple of rows in excel, populating them with manf# and letting KiCost do the work of finding prices for several distributors - would be very neat and fast.
A completely unrelated but pretty cool feature I can think of (which relates to the first point above):
It would be nice if KiCost would be able to take it’s output xls file and adding the manf/manf# fields to the local libraries, so one could use KiCost not just for costing an assembly, but also as a means to conveniently populate the local KiCAD libraries with the manf/manf# fields.
Might even pay off to add the option of custom fields via KiCost to have them added to KiCAD (like internal whatevers) or changing field values (it’s easier to rename devices when you can see all of them underneath each other vs. if you can only do one-by one in KiCAD).
But maybe this should be better done with a stand alone lib<>xls converter that works both ways?
Ha, right back at ya!
Your script/prog saved me a lot of confusing and error-prone manual copy&paste to get the right amount of devices for my boards. I’m sure I’d been able to come up with some sort of python script on my own, but KiCost is already doing this job - so big thanks for saving me a lot of work.