Please keep in mind that these are $0.59 steel molds -- they are cheap and they are rough, but I have had great performance out of mine, with NO sticking using paraffin waxes.
To clean to grease off, separate the tins apart, remove the packing peanuts between the molds, and then put them in the sink and fill with boiling water, and add some dish detergent or degreaser (Greased Lightning, Purple Power, whatever). Let them soak, then scrub them out really well. I had no problems with the grease after that.
Also, the way that these are made is going to cause some metal discoloration -- it is from the heat treatment of the metal.
Anyway, great molds, no problems at all with mold release, even without release spray.