This is my current process and formula for making blocks for printmaking.  For very detailed blocks and engraving , the "Top Layer Calculation" below is based on the recipie for Resingrave.  The Resingrave blocks that Richard Woodman made had a thicker layer of resin at about 1.5 mm, I am currently trying .5 mm..  You can use this calculator by copying Google Sheet to your own Google account using the link below. The formula that Richard Woodman developed used a 4:1 type epoxy, I am using 1:1  (Hardener/Resin) here so you will need to adjust based on what you are using.

Sealer

For blocks that do not have a lot of detail the seal coat alone seems to work well for mokuhanga and western printing techniques.  It also hardens the surface plus waterproofs the MDF.  Here is a a video of preparing a block using just the sealer.  

NOTE:  If you are doing the second layer with the Resingrave coating then you can skip the skim layer of  fast set drywall compound.  

NOTE:  The seal coat reduces the bubbles that come from the air trapped in the MDF ( or any wood) when pouring the "resingrave".

NOTE: Recently I have first sealed the MDF with the "seal coat" in the worksheet, then sanded, filled with fast set drywall compount, sanded then sealed again with with the "seal coat".  The second sealer over the filler will require about 1/3 of the calculated amount used in the initial sealing of the MDF.