All the things you will need:)
Start by painting your rock completely white. This is a base color for the minion and will make the other colors stand out.
Now paint the rock yellow, but leave the bottom white because we are going to paint the minion pants there.
Now paint on the pants of the minion with dark blue. You can outline it with a pencil first.(front view) do the same on the back of the rock:)
This is how it should look at side of the rock. Make sure it's even!
now paint on the straps on the side of the minions shirt. ( draw a line connecting the 2 corners of the square) then add in some details with black(hair, gru sign)
Now draw the minions eyes and goggles!:) and also the arm and gloves.
Then paint the rock with a layer of gloss to protect the colors and make it vibrant:)
Then your done!
Comment below if you have any questions:)
Tips: -wait until the paint has dried before painting something else on it. -DO NOT use washable paints. -it's best to use a smooth rock:)