A lot of things have changed. I last built models 40 years ago.
I would like to know exactly what a wash does?
Panel lines can be highlighted to create shadows and depth to your build, like an airplane’s many different panels. It adds realism to the subject. Washes are used to add layers of dirt rust and grime to your model, over the top of the models paint. There are many good threads on this subject in these forums. I encourage the use of the search bar for this. Youtube is a great source as well.
@alhen13 welcome to the forums. What types of model are you focusing on? As mrb865 mentioned, there are great videos and advice available if you want to research. It also depends on how dirty or weathered you want your model to look. My first few focused on getting them put together and painted so they looked like real aircraft would look straight from the factory. Since then, I try to add some different techniques on each model to see what I can do and whether I like how it looks. I’m a minimalist when it comes to weathering but others take great pride in dirtying up their creations.
I am starting out very easy with Tamiya V-1 German buzz bomb. Not much to it. But, I try to be perfect with each build. After that I am going on to Revell F4U-4 Corsair.
As an ex-submariner I am going for military craft above the waves.
There are some great videos detailing how to weather the Corsair. I highly recommend deciding which plane you want to build and researching it to see where you need to weather it. Some builders spend a lot of time pulling together all the images they can of the specific plane they intend to build. Have fun and good luck!