Add thick paint to a drawing

What can we use if we don't have palette knives or thick (heavy-body) paint?

Use a sturdy plastic spatula, old credit card, or butter knife as a palette knife substitute and thicken regular acrylic or tempera with a little modeling paste or cornstarch so you can 'scoop a thick dollop' and spread it with firm strokes.

My paint keeps sliding off the paper or canvas when I try to spread it — how can I fix that?

Press down and use firmer strokes with your palette knife or substitute, apply smaller amounts of thicker paint (less water/more modeling paste), and let each textured layer dry flat for several hours as the instructions say so layers will hold.

How can I adapt this textured painting activity for toddlers, school-age kids, and older kids?

For toddlers use washable tempera on heavy paper with big found tools like spoons and cardboard and close supervision, for school-age kids introduce palette knives and comb textures from the 'Press or scrape the wet paint with a found tool' step, and for older kids use heavy-body acrylics plus modeling paste and multiple 'Add another color on top' layers to experiment with texture and color.

How can we enhance or personalize the finished textured painting?

After the painting dries flat, add varnish or glue-on found objects, sprinkle sand or glitter into wet areas for extra texture, or photograph and lightly edit the image before sharing the finished textured painting on DIY.org.