As usual, I am working on several paintings at once but they all look a little flat so I am injecting some texture into them.
The best way to do this is at the beginning of a painting is using gesso or modeling paste. You can also use these on an in-progress painting but, as they are opaque, you will lose any colour already down.
One method I enjoy using, because it brings up a lot of unexpected surprise, is laying down two, three or even four layers of acrylics on top of one another and then scraping through the acrylic.
Use thick paint for the best results and wait for the paint to touch dry before adding another layer. I like to wait until the top layer is just touch dry before dragging the scaper through the paint. The effects are different according to how dry the paint is. Practice this to see the different effects. The wet paint also lifts off some of the dried paint underneath, giving interesting results.
The first photo is the work in progress. The grey is layered on top of the cream which is on top of the base painting colours and the scraper has been pulled through the paint.
This is a closer look at the texture achieved.
In this photo I have added another layer of blue to the top right hand triangle and again dragged the scraper through the paint.