Hi Robert,
I don't know if this will help or not, but one technique I ran across (that worked really well with some beginners ) was to have the student memorize only the 6th string first, using the fret markers as the main guide posts. (i.e. test them on the names of notes at the 3rd, 5th, and 7th posistions first. Get those down, and them have them figure out where the other notes are relative to the ones they have memorized. (ie. C is 1/2 step above B, and F is whole step below G)
After they have that down and are able to cover most of the sixth string notes (even if it takes a few seconds for them to figure out where a note is), then have them memorize notes on the 5th string and 6th string together. In other words, make them memorize groupings of notes such as (C is the note on the 5th string just below G) and (D is the note on the 5th string just below A ), etc. Then assign a word or phrase to help them memorize these groupings. For example, you can use the word "Go Car" as a way to remember that G and C are adjacent to each other on the 6th/5th string 3rd fret. In a similar way you can use the word "After Dark" as a way to memorize that A and D are adjacent to each other on the 6th/5th sting on the 5th fret, "Big Elephant" can be used for B/E on the 7th fret, and so on. Use these fret marker places as a starting point to have them learn all the notes on the 6th/5th strings first, then work your way onto the other strings gradually.
Maybe this technique can help as a starting point? I find that most people can memorize the 6th/5th strings over a few weeks since they can put it to use in playing barre chord progression when they know where all the root notes are.
Once they have the 6th/5th strings down, then you can move to the 4th string, and use the same technique of memorizing these notes relative to the notes on the 5th string that they already know, instead of forcing them to learn all of those 4th string notes from scratch, all at once. Along the way you can start to introduce the idea of octaves and show them that they can also determine the note on the 4th string based on note on the 6th string two frets down. Basically teach them how to build a knowledge of the fretboard based on information that they already know, and keep building it up little-by-little.
I hope this is helpful.
-- Jim