Hi Mark,
I'm by no means an expert, but other dyes just don't quite produce exactly that same type of glowing color. I have a UK forum thread saved in my favorite's here at work where a guy used Jaquard sun yellow for some materials, and mixed that with a little chartruese for some other materials to come close to picric dyed stuff. It's saved on page three so you have to go back and forth to read the entire thread.
http://www.flyforums.co.uk/fly-tying-fo ... cid-3.html
You don't have to heat the picric solution or need to set the dye with it either. Just clean the fur or feather, soak it overnight to a day or two, rinse well with water and dry.
I sort of got tired of always looking for this and that dyed with picric, and just reading about more and more materials that used to be dyed with it, so I bought a couple of liters last October. This is already in solution so you don't have to worry about messing around with the dry crystals. The only drawback to it is that the shipping is about the same cost as the liter is. The guy's name is Pete, and he's been selling it for quite a while at eBayUK. Here's a link
http://cgi.ebay.ph/Picric-Acid-Saturate ... 20aa73ccf0
Regards,
Mark