Burnt marshmallows work excellent for giving the appearance of Burnt Skin. Burn the marshmallow- peel off the burnt area- open and apply to skin when cool enough to handle.
To easily create the effect of scars, Combine pink & green facial tissues in corn syrup, allow to soak and apply carefully. Let them dry before adding any make-up.
Also, various colors of craft tissue paper work well too
Get a band-aid about the size of the boil you want. Then, dip some tissue (toilet paper works best) into a mixture of PVA glue and water, and form it onto the band-aid. Make a groove by pushing a pencil about halfway into the tissue. Wait for it to dry and cut around the hardened glue and tissue. Peel the backing of the band-aid off and place it in the desired location. Use makeup to blend it onto your skin