How to make Texture Paint

1) Find a suitable container. Airtight is best.
  Put some PVA glue in it. A big dollop is good.

2) Add some paint (not as much as PVA glue).
Something like a 2:3 ratio would be fine - it's not rocket science.
Which colour isn't too important. Here it's a sand colour.  

3) Now add some texture. Here it's table salt being used.
If worried about salt dissolving, perhaps use different types of sand instead.

4) Use a cocktail stick/toothpick and mix the ingredients together.
Add a few drops of water to help bind it all together.

 5) Here you can see that not enough salt was added and no texture can be seen. It just looks like paint. 

 6) So add more texture (quite a bit). Add it gradually and mix to desired thickness.

 7) There is now enough grit in there to make a nice lightly textured paint. 

8) Being added is extra slightly larger texture (shattered granite).
This will make the paint more suitable for bases and rubble.

9) Give it a mix and lift out the mixing stick. Inspect the stick, as this will give a better indicator as to how gritty and how well mixed it is (heavy particles will settle towards the bottom). Once you're happy with it, date the container!

 10)    To apply, use either a stick or old brush.
Mix contents and then dab/paste/smear the area with the texture paint.
Just a little was used here to help merge the grave stones to the base.

Hope it helps