I have been using tungsten beads in gold, silver, copper and black. I prefer the slotted beads which are ( in my opinion) easier to put on the hook.
I bought some jig fly hooks and tied a few up. I use sizes 8 & 10. On the #8 I use mostly 5.5mm (1gram) . 4.5mm (0.58grams), 4mm (0.46grams). On the #10 I use the 4mm.
I fish them with a 6' 6" lure rod with a casting weight of 0 - 5grams. I use 5lb Power Pro braid. So far they have been very successful. They certainly cast out well with a light outfit. My most successful jig fly is a gold beaded (4mm) version of a pheasant tail nymph in size 10. The last time I was out, which was a few months ago I must have had about 40+ perch from my local canal in a short two hour session. Most were in the few ounces range but I did catch one of 1.5lbs.
If you tie with the slotted tungsten beads it is possible to use ordinary hooks tying them so the bulk of the weight of the bead will ensure that the hook swims upside down, which helps to minimise any snagging on the bottom, as well as giving a better hook up.
I buy my beads from this company -
http://www.tungsten-beads-plus.com/collections/tungsten-products -
If you look at their website they give some very helpful info on hook sizes and the appropriate bead size. Sorry the measurements will be metric but I am sure if you 'Google about' you will find a conversion chart. Incidentally the beads look a lot cheaper in the USA.
I also tie up small slotted 2mm (0.055gram) tungsten beaded pheasant tail nymphs which I fish using a Tenkara rod. Only just started that but I did catch a small chub (coarse fish species)
David