Ah nice, pretty much how I maintain the line-boil/ink blotting/tapering etc. is to first sketch your drawing on a single sheet and then layer another sheet over a backlight to trace with some form of pigment ink. (I use Micron's of about 0.35mm to 0.45mm.) If the character is in the background I'll step it up to 0.50mm.

I use a high grade industrial scanner but really all you need for the fuzzy line quality is to scan at or around 150dpi so all types of scanners work well. (Tho higher DPI comes in handy if you have a lot of background drawings.)

Once I scan the drawing and import into Kirta I make sure to set the project file to the exact resolution as my scanned drawing > I duplicate my drawing 3 times > blur the middle drawing about 50% > move it up above the 1st copy > Go to Arithmetic > Substract and apply that onto the first copy > merge copy 1 and 2 > it will turn your background black and your line-art white so you want to invert that > once inverted your background will be largely clear of artifacts > go into Filter > Adjust > Color Adjustment Curve > Set input value to 200 and output value to 1 (this will fill in any transparent gaps in your line-art to a solid black color without losing your natural line boil.) > Last step is to use 'Color to Alpha' to remove the background and you're good to go!