I use Clip Studio Paint Pro and I use the brushes that come with the program (like "Gouache") but this is a list of downloaded brushes I use regularly. Some of them have versions for other drawing programs as well! 

TIP: If you find that some brushes are laggy, try only using a smaller brush size or making the stabilization lower (0-10).

(FREE) RAZOU linearter by Razouru

Content ID: 1705963

(FREE) Tone Brushes by seinotaph

Content ID: 1835931

(FREE) Artemus Pencils by artemus 

Note: Specifically ”Artemus HB” 

Content ID: 1758182 

(FREE) small shaky brush by rork-s 

Content ID: 1916979 

(FREE) Raz's roughy sketchy set by Razouru 

Content ID: 1738915 

(FREE) CAREFUL, CUPID! - SCATTER PENCILS by fleshrats 

Content ID: 1991252 

(FREE) 24 Realistic Ink Pens by saturns_day 

Note: Specifically “18” and “23” 

Content ID: 1904574 

(FREE) CSP (MS5) Brush: Side Pencil by Ron Chan 

($1) Scratchy Scribbler brush for CSP by pikozumo/kozmo 

(FREE) Sketchy pencil by ReneeGee 

Content ID: 2022981

(FREE) SCRIBBLERRR (Take 2!) by fleshrats 

Content ID: 2036817 

(FREE) Meckie Pencil by vforvignetta 

Content ID: 2059164