imo hot mud setting compound 2o,45,90,would be to hard for a diyer even for the experienced unless your working with this stuff daily. ok you can use it to fill dents, gouges, holes ,low spots .but for skimming i would use all purpose joint compound .thin with a little walter you can even roll it on with a 3/8 nap roller then smooth it out with your 12 inch blade their is a skill to this start out on small area and work your way up.dont rush dry times prime with a latex primer sealer and paint latex at the big boxes lowes they have books on drywall finishing about 20 dollars ,or just stand their and read it