This is how Polystyrene eggs are felted:
Lay a thin but opaque layer of wool fleece on the Polystyrene-egg and felt it with a multiple dry felting needle . The small barbs at the end of the felting needles make the wool fibres interlock with the Polystyrene. This creates a stable connection.
Extra tip: Felt one half of the polystyrene rice first, then the second half. Lay as many layers of wool fleece on the egg until the Polystyrene is completely covered
The narrow lines with very thin wool strands are felted with a single felting needle. To prevent the patterns from slipping, before Felting fix the wool strands with Pins .
The round dots are created by rolling some wool between the fingers into a ball and felting it onto the egg from the centre outwards. 
