Are you wanting to make this scene memorable and different from what the students might already know? It's difficult because the blood in the scene is imagined (albeit it is, of course, a remembrance of the real blood of Duncan).
How about changing the lighting on the character (you?) to reveal the difference between what Lady Macbeth sees and what everyone else sees? How about using some "real" fake blood (ketchup would do nicely) and light her with a strange color, ... let's say red just for fun, ... while she imagines her bloody deed. You could wipe that stuff all over your front after you wring your hands together many a time. Then say your lines:
Out, damn'd spot! out, I say!—One; two: why, then
'tis time to do't.—Hell is murky.—Fie, my lord, fie, a soldier, and
afeard? What need we fear who knows it, when none can call our
pow'r to accompt?—Yet who would have thought the old man to
have had so much blood in him?
There are many times where, depending on how you want to act the scene, the transition could occur. My suggestion is that our transtion could occur when the Doctor says, "This disease is beyond my practice. Yet I have known those which have walked in their sleep who have died holily in their beds." There is a long exchange there between other characters, enough for you to make the change.
Behind you, have a bowl of water and be wearing a second tunic under your first. When you change the lighting back to regular white light, you could turn around quickly rinse your hands and pull off the soiled tunic to reveal that none of this really happened. Imagine some real fear and despair when you complete your lines:
Wash your hands. Put on your nightgown. Look not so pale.—I tell you yet again, Banquo’s buried; he cannot come out on ’s grave.
I agree that this scene would benefit from some individual inerpretation as it is so well-known and for many audiences frames their thinking about Lady Macbeth as villain or victim.
The handwashing is of course central, and perhaps considering what else she may wish to make 'clean'. Perhaps more of a bathing/showering scene might help to show how overwhelmed she feels with the blood of her victim. She could of course be clothed during this scene to emphasise her sleeping state and tortured mind.
This is a popular scene. Everyone will know it instantly. It's part of our culture. I suggest you make it your own. Interpret it in some new and different way, with an off-the-wall version. Take the elements that stand out to YOU and focus on brining those out.
A couple of things need to be established on the outset. The first would be to understand the implications of the scene. Simply put, the sleepwalking scene is one of the most important in the play. It is seen as a "gold standard" for actresses that wish to represent the very best in drama. With this in mind, I would ensure that you grasp the magnitude. I think that being able to capture Lady Macbeth's fundamental state of mind is going to be one of the strongest challenges you will face. There are a variety of emotions that you face in this scene. There is regret, frustration, insanity, guilt, as well as a type of compulsion that have to be brought out in the scene. The idea of a collection of emotions is critical to the scene. I also think that it might be important for you to bring out the certain empathy in Lady Macbeth. Historically and from a literary point of view, she constantly gets the negative response and ire from readers and critics alike. She is blamed for triggering Macbeth's murderous rampage. Yet, this overlooks the fact that both she and Macbeth coveted power, not simply her. I would bring this out in my depiction of her and the interpretation of this critical scene.