I gave a workshop last month where we painted grapes and leaves using several fun texturing techniques.
The first step was to wet the paper (you can wet both sides to keep it from drying so quickly as you work) and paint wet on wet the colors you want for the grapes and the leaves. Have a general idea of composition and placement when you do this. While the paint is still wet place grape shapes cut from wax paper in the areas that you want the grapes. As you place several shapes you can add more dark paint around them and then place more down (adds depth). using real leaves paint several colors on the back side (where the veins are) and then place them on the wet paper, press thyem down and leave them in place. You can also use strands from cheese cloth to put on the paper (add more paint on top if needed) to suggest the vine tendrils seen with grapes.
If your paint/paper starts to dry on you just spray it with a fine mist of water. You have to work quickly at this stage so be sure you pre cut enough grape shapes and have your leaves and cheesecloth ready to go.
Leave everything in place and let the paper dry completely.