concept phase :
drawing and sketchUp
drawing for proportions, sketchUp for general dimensions. I usually go back and forth until I'm pleased.
I use a lot of the resources of this forum, because they tend to be more accurate
I like to draw in either 2 point perspective or a losely isometric perspective.
cad work:
solidworks in the past but migrating to fusion360 , and I export to sketchUp for 'virtual prototype', since sketchup has a lot of acurate parts to download, its a fairly acurate preview of how things are going to fit. Grabcad is a great place for resources as well for cad files.
cad model exported to sketchup : you can see that all parts are for the final thickness and it has all the fitting in the right places. its very acurate
for 3d rendering I use keyshot, but there are some plugins for sketchup as well and I think it should be easy to find a free one.
I've tried blender once but the setup is too long, so I'm trying to find a better option.
if you use fusion as a cad program, it can export to sketchUp and from there building a scene or getting parts into for render should be very easy
for prototyping and personal projects I used mdf and I still think its a great material for personal projects, its cheap and stable. doesn't last too long though.
General tips:
I don't think drawing is a entirely necessary skill with case design, but it certainly helps A LOT and make trying out options a lot faster (if you know the basics)
the skills needed for product sketching are really foundation techniques so Its really easy to get the basics but mastering it takes time of course. if that's close to your career goal (or is something you are interested in doing), I think its something worth pursuing.
see if you have access to some design sketching books on a library or something. they help a lot in getting the basics
edit:
here in the forum there are some great tutorials for basic dimmensions, read it all up
https://smallformfactor.net/forum/resources/categories/guides.9/