I cant seems to do it smoothly and i don't know how to "grab" the coin from the last finger with my coin...Any tips?

Grab the coin from the last finger from your THUMB you mean?

You neeed to balance it on your thumb. Its not gonna be easy at first, but keep trying. you will keep dropping it, but after awhile, it'll become smooth.

1) Make sure that the sides of your pinky grab more surface of the coin
2) Your first 4 fingers extend outwards while your pinky goes sort of downwards. ( this way the coin at your pinky gets closer towards your thumb when it reaches out for it)

Generally just remember the scissors like movement, 4th figner moves upwards, pinky moves downwards, and thumb reach for the coin from beneath.

My 2 cents worth.

Perfectly normal if you are unable to do it smoothly if you just started off with your coin roll for not too long. Because it simply take some practice before you start dropping your coin lesser when you roll, in another word, improve.

When I first started off with coin roll, I did it with a half dollar which I find it a good coin to kick off with as compared to singapore 50 cents. Reason being it got the size and the weight. When you can roll half dollar smoothly, then proceed on to singapore 50cents. I feel that its easier this way. By the time you can roll 50cents smoothly, you should be able to roll just about any coin, even 20cents is possible.

As for 'grabbing' the coin. You got to grab it using your thumb when the coin is on your ring finger. When you roll the coin, it will first land on your first finger, then middle finger and lastly your ring finger. When it is on your ring finger use your pinky to push it down and that is when you extend your thumb to the bottom of your fingers and place the coin on your thumb then bring it back to your first finger. And repeat the process.

Just keep practicing, don't be discouraged when it drop all the time, its a process to success.

Just my opinion.