This is a true story.

Don't let the pre-amble intimidate you, it's not as hard as it sounds. You will need:

Painting software with some image editing capabilities. You don't need all the bells and whistles of Photoshop, but I wouldn't recommend something like MSPaint, at least not to start with. I'm using Clip Studio Paint.

A really beat-up paper texture. The grungier, the better.

A lightly-textured brush. Here are the specific brushes I use, 99% of which is the well-named rough brush. Try and avoid anything with any impasto elements.

Go to your colour-picking tool and use the 'select from layer' option. Doing all the painting on a single layer is going to make your life easier.

A complete willingness to make mistakes and, instead of erasing, painting over them. It generates much more colour variation and interest! Keep your finger off the E key.

Good reference! That painting is a master copy of Mitchel Hooks' art for Day of the Ram. Find a style you really love and want to learn? Have no clue where to begin? Do direct studies!

Let's not worry about whatever is happening in the background. It's probably fine. Let's get started! Pulp magazine art is a lot more varied than you might first think, so don't agonize over having a style that 'fits' or not. I'm also specifically aiming for something you'd see on the cover after printing, not the initial painting they would use for printing. The stuff I'll show here is a pretty narrow band of it, but here are some general commonalities. This is a painting by Tom Lovell.

Let's dig into this.

The colours are very bright and saturated, but the actual values, the relative lightness and darkness of them, are actually grouped very simply! You can check this by filling a layer full of black, putting it on top and setting its mode to colour. If the value of a painting looks good, you actually get a lot of leeway with colour. But here's what I think is the most important thing to keep in mind.

The darks aren't that dark, and the lights aren't all that light! Covers are paintings reproduced on cheap paper. Anything you wouldn't want to happen in the printing process, you lean into. Value wash-outs, lower contrast, colours getting a weird wash to them, really gritty texturing. So let's get painting! Here's my typical setup.

That bottom folder is the painting itself. The screen layer is the grungy paper texture. To get the effect you want, put it down, invert its colour, then set it to screen. That washes out your painting far, far too much, so to compensate, I put a contrast layer up on top. Fiddle around with the settings, but this is where mine ended up sitting.

Note I'm saying this before even starting the painting: you want to do this as early as possible. This is where the 'select from layer' colour picker comes in handy. You can paint without worrying about the screen or contrast layer. Something not looking right? Enable your value check layer and keep painting. When you turn it off, it'll still be in colour. Here's a timelapse so you can see what that looks like.

And when you check the values...