Depends on your stats and the master that you go to. I did it years ago, but from what I remember it was pretty easy.

It is actually pretty quick, Smoking kills is an easy quest that should not be hard (refer to a guide if you want to make sure). The helmet is pretty easy some people have different methods of getting points,

Example - Vannaka for 9 Tasks; your top slayer master for the 10th to maximize the points. In that case the first 5 give you 0 (unless you've done 5) then the next 4 will give you 4 each and if you say go to duradel the 10th task will give 75. Or if you have duradel you could just visit him each task for 15 points and eventually a bit slowly get to 400 or if you're near 50 tasks you'll get like 225 points off of him. Depends on your slayer master and how quickly you will do your tasks.