Hi Hingol,
Good question.
Still use a sinker as you normally would...or would not.
Length of the leader will depend on a number of factors. But in real terms, for day to day fishing, what ever length you have is the right length
Shop purchased leaders often come in sizes at 20cm 45cm 60cm 90cm.
You can purchase DIY rolls of steel leader that come complete with crimps. They are usually available in 10 meter. 20 meter and 30 meter rolls.
Fish can smell...and I don't just mean when they have been left in the sun all day ...A blood hound can detect by smell a good 12 inches (30cm) into the ground. So you really need to bury that murder weapon a good 3 or 4 foot down .
Some studies have shown that some fish have a sense of smell some 10 thousand times more sensitive than that of a blood hound. Some fish, like sharks for example, have been shown in research studies, to be able to detect a few drops of blood in the water from several kilometers away.
Steel will and does react with salt water. Even stainless steel. It has an electrolysis reaction. Fish can smell it...all fish can smell it....So, the steel leader should be coated in nylon.
The reason for a steel leader, or as we call it here in Australia, a trace. Is to stop the toothy fish biting through it or cutting you off on rocks. Many sort after reef fish are ambush predators. They open their mouth and simply suck in what ever it was they were targeting...including 20 or 30 or 40 cm's of your line. Then the jaws of the ambusher come crashing closed with line cutting force...and it all happens within a fraction of a second.
So steel trace or leader when reef fishing, in my opinion is a must have.
itsaboat mate...Life is just a boat and then ya marry one !