I'm stuck on Step 70 of HOJYO Takashi's Buddha... what does the diagram mean?
As you found yourself Google Translate was not particularly helpful in this matter:


  By overlaying the more because What is the other side 
  
  ` Ru to one representing the thumb of muscle 
  
  To SenWataru and ho stick base of Ne亢layers of trout
  
  Although a state of twisted without breaking the non- g was Li 
  
  Only to cowpea in the following figure around the hand of Saki珊 
  
  Become good long as )


And using the camera-based Google Translate, we get:


  To represent the muscles of the thumb by overlaying more flipping and to the opposite side (but better at the root of this layer is to state that twisted without breaking the perfect interfere with the base looks like the following figure only the peripheral of the hands of the tip it is sufficient)


I approached the users in Japanese.SE chat for help with this. This is a wiki since the work was done by broccoli forest who is a user over there. It was translated as:


  roll up a layer and cover up opposite side with it so that visualize thumb's muscle 


Note though, by that users admission, he is not familiar with origami.