The trick to getting the rivets to go in is to push the panel(s) tightly to the metal behind it-  you don't want any gaps.  Then put the pin in the rivet head a bit and carefully get all 4 legs through the whole thing and press the pin in until flush.  There has to be a tool to help press the pin in?  You need three or four hands to get the stuff right (or some luck)  I've been using the handle of a stubby screwdriver.

 

For the price of these rivets, you ought to get a bunch of extra pins with it.  I've tried the 4p nail, and it tore up the rivet (it's too hard for the old plastic)  and takes too long to make (cut the nail in thirds, grind/sand the ends and burs smooth)   So I'm sticking wit the 3mm wood dowel pins;  you get 50 or so from a 1m length for only $1.

I know that this is a really old thread, but I found a substitute for the rivets. (Those of you looking for originality need not apply.)

Anyway, I got them thru Zoro.  (Part #G5101564) for $8.83 + shipping. I haven't seen fasteners this small anywhere else.

I like those, good idea!