Do I need to prime a flat paint before repainting with an egg shell or satin… also in the bathroom do I need a different type of paint?
No need to prime first as long as you are using the same type of paint, latex or oil base. For the bathroom, a good 100% acrylic interior paint with a satin or semi-gloss sheen is fine. If your bathroom has limited ventilation use a semi-gloss sheen. The higher sheen is more resistant to humidity and moisture.