I use lead shot - bought from a fishing shop in Southend, recommended by Ruark! It's cleaner than sand and easier to experiment with.
You really need to listen and judge for yourself. Too little loading and the speakers sound sort of bright and light - too much and they start to sound sluggish, a bit heavy. Get it right and you get a firm but "mobile" articulate bass.
I have no note of exactly how much weight I put in each speaker, but I think it was something like 1kg to start with. Then I borrowed (no jokes please!) a pair of my gf's tights and loaded them by putting in 100g of shot then tying it off, and then adding another 100 and tying it off - I repeated this until I felt things sounded right. Eventually I created what looked like a nylon string of sausages! This also has the advantage that you can just remove the "tights sausage" of lead shot and go back to scratch at any time - if you move the speakers about or get a new amp etc. ALSO.... by putting a little piece of cotton or string on the end, you can just pull out the whole caboodle whenever you want.
Talismans are indeed "mercurial". They are very sensitive to every change you make to your system. That also means they are capable of much better sound than you'd first think.
I still want a pair of Crusaders though.