We worked on section drawing lately. Basically, section drawing gives an iformation which cannot be seen from the outside. Actually, it is kind of expressive drawing in terms of detalied information. Hatching parts in the section drawing are giving the information of cut line passed there, more basically it can be think as a knife and surfaces which was cutted by knife has to be hatched.
There are 4 section in the drawing, in my opinion the important thing is using referrence lines properly and to pay attetion line quality. Also in this work we did not care about line hiearchy because the model divided 5 parts and it is not valuable and unnecessary to give that information. Actually, I did not hatch the section parts, I painted which was not a good decision for this kind of work because paper is much more getting dirty. As a suggestion use hatch technique with 45 degree strick lines but pay attettion to use frequent lines.