Cirrus Painting + SAI questions

[~Master~ Button Mash 2,308]

Broke out my old Windows machine and did a little work in Paint Tool SAI. Tried doing a painting of Cirrus. It came out...alright. I have a few questions about SAI, thought.

 

1) What's the best way to get straight lines and smooth curves? Is it just a matter of practice? I tried experimenting with line-work layers but they're limited in terms of fill capability.

 

2) What's the best way to add shadowing effects? Thin airbrush? Lighting effects?

 

3) What's the best tool to use to add more detailed manes?

 

 

 

Just a trace of the pony creator image. Took about an hour.

I don't mean to bump my thread or anything, but I'm really perplexed with certain parts of Paint Tool SAI and would like some advice. Edited December 29, 2012 by StratoPegasus