I'm just moving away from Eco Flow to Fiebings. What a difference, my word. I did a test piece of Eco Flow black dye on one side and Fiebings black dye on the other. Eco Flow side is extremely dull, grey and blotchy. The Fiebings goes on completely uniform as a deep, shiny black. I used one of those cheap sponge brushes with the wooden handles.
I wish I'd known in the first place before buying all that Eco FLow stuff. Though I still like the stains and antiques for now. I also worry the chemical stink of the Feibings dye now that it's too cold to have my windows open at night.