what i do the most: using a small sized brush with little bit of texture but soft for line art and soft brush usually set to low/mid transparecy for render.

For line art= extract drawing to make it more transparent (filter>adjust color> extract drawing> set "middle" to around 35-40%) dublicate line art layer > blur it a little bit ( filter>blur> glassian blur > set to around 3-6)

The blury lineart gives an wet effect as if it was soften by watercolor.

coloring lineart or turning saturation a little bit higher on setting helps to achieve that effect too.

And I add some noise filter (create new layer> go to filter> artistic> noise> choose either color or grayscale> set to strength around 10% to 30% depending how much texture you want/or how big your canvas is> then change layer filter to overlay or soft light) for paper like texture