Some simple things i think could help sell the illusion of growth, at least in spurts would be (you would need a non-growing other person), simply start the scene with the other person standing on a few books or an applebox or something to make them taller than normal. After the 1st growth spurt, simply have them stand on the ground like normal. Then, after another growth spurt, have the growing person stand on some books.
If you get enough (it could even be stone pavers or something), have a trail that taller person could walk on, so they're not just standing still the whole time.
A nice touch that Mistress Taylor has done in some of her videos, that also really sells the illusion of growth is showing the person actually getting taller, a medium shot where we can see their body inching up. I'm not sure what Taylor used, but it seems like it was more than just the actress standing on her toes, or moving from a crouched position. Some sort of lift.
Also, if you're thinking about using forced perspective, like Gary tries to use, make sure your eyelines match. Don't have one person close to the camera looking back towards another person far away who is looking forward. Yes, 1 person should be close to the camera, the other farther away, but if they're supposed to be looking at each other, then they should both be facing sideways as though they were the same distance from the camera.
But, I totally agree with what many others have said. Study the HBO 50 foot woman growth scene. Notice they used velcro on the clothes to get them to rip. Quick cuts. Different angles. Forced perspective and miniatures (which are quite expensive, so I don't expect those).
I also have a lot of film and VFX experience, so any questions about keying or general visual effects or filmmaking, let me know.
Here:
https://www.youtube.com/watch?v=F_6sn8AeSVw#t=245 is an example of effects I can help with. In this case it's shrunken male and growing male (around the 4:40 mark), but it'll give you an idea. Just let me know if you'd like to know how I did them.
-
Jamball