Wet on Dry and wet on wet are easy to achieve with acrylics. Apply a fairly neat colour first, then gradually add more water to the wash as you work down the paper.
If we want a graduated wash then to achieve this after the first couple of strokes we reload our brush with clear water instead of fresh paint.
Each time we reload with clear water, the paint in the brush will be diluted somewhat, resulting in a graduated wash as you progress down the paper from the full blue at the top to almost clear at the bottom.
Allow to dry completely before you continue with any other painting.
Wet on wet
Acrylics can be applied wet into wet in exactly the same way as watercolours. Wet the paper, drop in spots of colour, then let these merge and spread across the paper. For a more controlled effect , quickly and lightly pull the brush across the area to be coloured. This is difficult to control but makes lovely clouds and can give the effect of rain fall if paper is slightly elevated to allow paint to run.
Blended colour washes are ideal for skies but they do need a lot of practice to master without it looking muddy. They can be worked wet on dry or wet on wet.
Is another water colour technique which can be used with acrylics. Apply a wash to the paper, then use pieces of dampened paper towel, cotton wool or sponge to lift out small areas of colour.