When I have used Epifill, it has ended up being a slight bluey, tan colour, was very hard to sand, was generally a bit disappointed in it, it did stick where I put it though & is still there many years after.
Make your own fillers, a lot cheaper than having half full tins of stuff every where. Mix required quantity of epoxy resin with Q cells for above the waterline and use phenolic spheres below the waterline.
Oh, and do not open container of cells or spheres if there is any wind or draft. And wear a damp cloth over your nose and mouth till the mix is homogenous.
The main reason for using the Norflex for me, was to keep with a quality system. ie,it is hard enough getting paint to effectively stick to aluminium and so I needed for the primers/fillers to work in conjunction with the finish paint. The last thing I needed was for the fillers and paint to come away from the hull.
I only used 25 kilograms of the stuff and probably sanded off 15 of that in the end.
Needless to say my 'popeye' arms were working overtime with the torture boards!
you always have good input Loose Change