Palette Knife Painting
Choosing a Knife
You're looking for a painting knife with a flexible blade that has a good spring or bounce to it.
A very stiff blade is limited in the type of marks you can make with it, and a blade that's too flimsy or floppy is annoying as you can't control it well (and likely won't last). Metal knives generally have far more spring to them than plastic ones.
The handle should be smooth and comfortable to hold. You don't want a knife that feels unbalanced.
The blade of the knife should be well attached to the handle -- you don't want it to rotate.
How To Get Paint on The Knife
It's just scrape the knife across the surface of the paint so it gathers up some paint, or dip it into the paint and flip out a bit.
Exactly what shape you produce depends on how much paint you had on your knife, and how hard you pulled or scraped it across the surface. If you have gaps between the bits of paint on your knife, you'll produce gaps in the painted area (as shown by the paint adjacent to the knife in the photo).
By lifting your knife from the surface you can create a little ridge of paint, which can be built up into interesting texture.
If you're working with acrylic paint, you'll need to work fast or add some glazing medium / retarder to your paint to give you more open time before the paint dries.
Thick and Thin
You'll get different results depending on whether you're using an opaque or transparent color, or a color with a strong undertone.
If you use a single, straight stroke, you'll get the two colors applied adjacent to one another. If you go over the stroke numerous times, or move the knife from side to side, the colors will mix, and that's when beautiful things can really happen!