Hello dear anon! No need to apologise, I don’t think anyone has asked me this question before, so it’s all good : ) Ok. So here is a list of methods on tidying up the line art and make it look more sharp, dark and refined. Hope this could be helpful to you and if you have anymore questions just let me know❤
The default Photoshop brushes are great and decent, hard round pressure is my all time fav. There are also lots of amazing resources out there that could give you really sharp and crisp lines. Kyle T's Brush sets for example [ Link ]. It’s great to be adventurous and try them out, find the brush that suits your working style(●´▽｀●)ノ. Here is a [ master post ] of all the related ask about the brushes I use.
I normally adjust the ‘levels ’ after I finish the line art, it helps clearing out the gray tones and sharpen the dark lines. You can access this function through image > adjustment > Level (or hot key command + L for MAC or ctrl + L for PC.)
This function is more complicated than levels but works very well too! You could also find it under adjustment.
P.S Sorry I couldn’t supply more information on the functions since I am terrible at explain stuff ; - ; Here are some tutorial links with detail explanation on the function of levels / curves and how they work.
Curves [ Link ] Levels and Curves [ Link ]
Lastly, other related ask regarding lines
Smooth lines [ Link ]