I decided to answer this pretty thoroughly so if you ever care about what kind of brushes I draw with, here’s the masterpost for it I guess?* Images/explanations under the cut.

I’m sorry I don’t really download brushes often, and when I do I end up not bothering with them??? Probably because I’m conditioned by these brushes I have already…

*it’s nothing special

This is my default selector brush #36, like an angled textured rectangle brush? …I modify it 3 different ways (basically three different brushes). This is the unmodified version, which I don’t draw with. All we’re doing here is modifying this brush, 3 different ways:

BRUSH 1 : pencil

Here’s one I used to draw with a lot because it has a nice pencil like texture?

Above in the image are the scatter options that I have set for this brush!

And then afterwards, I basically adjust shape dynamics > size jitter > pen pressure/ roundness jitter > pen pressure > minimum roundness: 25%

Then I also click the texture option! The texture I have set is the very first default (bubble?) texture on photoshop. The scale I set it on is 100% (or actually that might just be the default setting, I can’t remember).

Transfer also checked, and is set to opacity > pen pressure, flow > off (I never understood why people liked flow? never worked for me)

Here’s an example of what it looks like up close (oh god old drawing sorry): 

****

BRUSH 2: pencil brush with scattering removed

^ what the description says, literally. I just uncheck the scatter option, and the brush turns to this fine line, and this is generally what I draw with 90% of the time on photoshop. 

Here’s an example of how it looks close up:

I like it because the lines can be manipulated really well? IDK it’s just personal preference, but my tablet agrees really well with this brush so I guess that’s part of the reason why I use it a lot.

****

BRUSH 3: basically brush 1 and brush 2 with scatter unchecked, and transfer unchecked. It’s a solid black brush with similarities to the pen tool in SAI (imo).

It’s a pretty nice lineart brush. I don’t normally do a sketch layer so this is what I use to draw head-on with B&W stuff.

Here’s an example of how it looks close up:

****

PAINTING BRUSH

I basically take the boring default one and under brush settings, adjust spacing to 1% (lowest) , go to transfer and check opacity > pen pressure. I switch off and on the shape dynamics, depending on if I want pen pressure or not.

That’s all for Photoshop brushes…there’s nothing really special to them other than just playing around with random default brushes and finding what works for you.

As for SAI….

(uhh sorry my SAI language setting got messed up a while back and I never bothered fixing it…)

I’m not very good with the program at all so what I draw with is the default pen tool because I think it makes nice lines!

I don’t do a sketch layer on SAI either because it’s too tedious! Normally I just draw head on, but my lines are messier up close that way…

If you have trouble controlling lines, people have told me that the stabilizer tool (top right on the toolbar) seems to be a good option if you want better lines. 

uhhh hope this sort of (thoroughly) explains your question (and anyone else out there who has an inkling of interest), because nice brushes don’t necessarily have to be downloaded ones :{D