How to finish my sketches ??

[KuRensan]

So I've been sketching a lot with my Pen Tablet but those are only sketches and so I want to draw smooth lines but with a pen tablet that doesn't really work T.T so now I have some nice sketches but I don't know how to finish them

I am really open to new techniques so if you know something that really fits my drawing style I'd love to know ^^. Here are some of my latest sketches:

Spoiler

I made drawn them with Sketchbook which not have a smooth line option so I only sketch with it and will finish it with a other program. I own:

sketchbook
Adobe
Paint Tool SAI

 

[Aeladya]

Photoscape is a nice program to add some touches with. It's free too!

 

[Rydian]

Why not use a vector editor to "line" it?