A fun thing to do is take a picture and import it. Then you can trace it!

This is best done on some kind of grid background but having a ruler (or two) is usually enough.

One suggestion, print one or two layers first to check the fit. Iterate with that before you print the whole thing.

Another helpful thing is to start drawing things parametrically. This should be familiar to programmers. You're using variables and you want to design things primarily through relationships. This becomes a huge unlock because scaling your parts becomes much easier