Some tricks with acrylics, watercolour and pastels
If you want to paint realistic church window glass, paint the colours (i.e. red, blue, green, yellow, purple) then draw in the black leading then melt some white candlewax and allow a thin film of this to 'flow' over your glass whilst the paint is still wet. Then leave it to dry.
For an easy skin tone in watercolours use cad red and ultramarine blue with a touch of green added. Darken with burnt umber to various degrees.
For creating mountains in acrylics use a palette knife. Drag gently down one side of the mountain after loading with white paint and the paper will randomly pick up paint to create texture of snow or soil changes. Push up with the point of the knife to create peaks.
For brick walls blob brown, white, yellow and a touch of red and blue acrylic paint then drag across the page with a palette knife. Before this dries use the edge of the knife to create the pointing between bricks.
For clumps of grass in acrylics flick upwards with the point of the palette knife or downwards with the point to create tree trunks in the distant trees.