I would use Plumbers Mait instead of glazing putty in the mix, Plumbers Mait seems to be the same as putty but does not set rock hard, saves having to mix grease in to the glazing putty.
I use about a teaspoon of Red lead to a cricket ball size of Plumbers Mait, thin it with linseed oil.
Works well if you refill empty mastic cartridges.
Good tip I was given. Make up raw linseed oil and red lead 'paint' and prime the seam with it. Drive home the cotton (I assume you use cotton on the garboard seam) prime the cotton with the 'paint' then apply red lead caulk as per others mix tips. You want the mix to be nice and red - not pink. The idea is to stop the caulk from drying out - hence the prime. Make sure that linseed oil is RAW and NOT BOILED.
Ive been mixing the stuff for years and still dont know why the red lead is in it!
Nice colour though and of course its very toxic so must be good . A sensible idea is to wear rubber gloves.
Thats the reason we put red lead in, /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif
It will prevent the wood being attacked by any fungal spores, you are correct safety equipment is needed when using it, once you have lead in your system it stays there and cannot be removed.
I get mine from Traditional boat supplies an a tub, I then mix about 20% glazers putty and with each golf ball sized portion I put a thumbnail of grease into help it to spread. I paint the same day.......... well actually I haven't used any in a few years which is testament to the fact that his method works.