Hey, thanks for the message Daleth.
I'll answer first with the duration of the process, saying it really depends on my motivation and said drawing. It takes me around 8 hours to do something like that (I usually do it in 2-3 evenings seperatly), and yes, I like to be a bit rough, but that's also mostly because of photoshop.
I don't really like the increasingly soft and detailed style you can have in photoshop. It's a bit unpersonal and it feels too much like it's been done on a comp. So I like to be a little more loose, I put some details aside for a bit more energy
I usually don't scan, I draw directly..but I wouldn't say it's a very good thing. Most artists draw with pencils then scan it, but I guess you have to go with what's more comfortable for you. And finally, as for speed painting, yes, give it a try
i'm not really doing "speed painting" since i'm not very speedy
But I've done it before (the twi'lek, a page or two before, was done in one hour). It's all about shapes and colours I guess.