I normally make my own fondant - unless I need black or red, then I purchase pre-made.  Usually, I grab some Duff's because it doesn't taste awful, it is nearby, and it is relatively inexpensive.  BUT - this time I need large amounts of black, including some parts of the cake that need to dry stiff.  No amount of Tylose added to Duff's can make it non-floppy.  Any suggestions?  Thanks a ton!

AI got the best ever advice for that here on cc! I make my own gum paste, fondant and modeling fondant too and have the same problem with black and red. So, what I was advised is to put the pieces in the oven with the oven light on. It works wonders! Okay, sometimes it takes a couple of days (depending on the thickness), but the dry completely!!! Only downside is that you can't use your oven for a while, lol :-D

I've done that before but in this case the pieces that need to dry stiff will be ON the cake without the ability to have them dry separately before hand.  Thank you for the help though! :)

I haven't really explored the other fondant out there - does anyone have any thoughts on how satin ice, fondx, etc dries?

I make my own black and red MMF by adding candy melts of the same color.  This works really well and less gel color is needed.  I can then use Tylose and my fondant will get stiff

would marzipan work for you?

1 part mmf, 1/4 parts wilton candy melts, and add some black dye to darken it the rest of the way. Works like a charm every time.