try some clear nailpolish so all treads will stay together

Cut it on an angle, & use Thread Heaven. Works like a charm.

I know that quilters use beeswax for the cotton quilting thread to keep it from getting tangled. That might work for metallic floss too.

Those floss ends are just killers, aren't they? What I prefer to do is:

1. Do all your cross stitches first, without the blending filament, then go back over with the blending, which adds another, albeit very thin layer of cross stitch.
2. Always use Thread Heaven, which makes the tendency for the metallics to separate far less! Beeswax can be sticky and although I used it all the time, I switched to the less sticky Thread Heaven. Be sure to read all their directions. They make it last longer.
3. You can indeed thread a needle with BOTH the floss and the blending filament at the same time. Use Thread Heaven on both. Use short lengths, 8-9 inches at most. Make a tight loop of both, wrapped taut around the needle. Instead of trying to get those fly-away ends through the needle, put this tight loop through...it's what needlepointers do, to get wool onto a needle!
4. Give up blending filament if you want lots of bling. Move to the Kreinik braid. Read their info at kreinik.com to see which size to use for the count of your fabric. Just buy one to try, as it is pricey.
I am making Christmas stockings for my great-grandkids and using the braid.
Have fun! I hated metallics until I figured them out. It does get easier.

Great answer and tips, Su! The first metallic I used, I remembered your advice--I am fearless!!! :)

Su, I'm going to try your suggestion about doing an additional half-stitch next time I'm a-blending! Using one needle for two threads (floss plus a metallic) I'm liking the thin Glissen Gloss threads in my experiments for a project I'm kitting (Mom's birthday).

I've used Thread Heaven, Thread Magic, and beeswax on metallics. Alas, it's an imperfect world in my stitching life. Beeswax tames the end of metallic braid like a charm, but doesn't help me much when combining threads. If I could only take one thread conditioner to a desert island, I'd probably go with Heaven because it really helps me work with one-needle metallic braids and cotton or rrrrayon floss. I don't use it with silk floss...

HTH and happy stitching to all.

Sunlander, forgive me for not making a direct reply to your question. I always use a needle threader when combining threads, and make a waste knot to start. A larger needle helps, but I can't recommend a size without knowing your fibers or fabric. I know many people think that testing threads and fabric is boring, but when you consider the money and time spend for a nice piece, it's a good idea. I keep a 8x8" frame for playing. And sometimes it's just what I need to end a day, when I'm too tired to count or try new techniques.

I don't like kreinik so I use Light Effects.

I want to thank everyone for your advise on blending filament. I have been working on 32 count linen (2 over 2). There is a fence requiring 3 strands of Kreinik Blending Filament. I tried using one strand at a time but would loose my place. I tried using a larger needle and it seems to be working out much better.