Use overlays well
Short guides that get to the point. Each one ends with something you can do in the next five minutes.
How to add film grain in Photoshop (the right way)
Use a grain plate on 50% grey in Overlay mode. It is faster than the Add Noise filter and looks far more like film.
Screen, Overlay, Multiply: which blend mode for which overlay
Black disappears in Screen, white disappears in Multiply, 50% grey disappears in Overlay. Pick the mode by the overlay's background.
Add dust and scratches to a photo in Photopea (free)
Open the photo, place a dust plate, set it to Screen. Three steps, no Photoshop needed.
Make a halftone print effect with a PNG overlay
Place a transparent halftone PNG, set it to Multiply, recolour the dots. It takes a minute and needs no plugins.