You’ve now got several very-good strategies here for creating foam. And seriously, I wouldn’t “over-think it” too much. If the texture has just a little bit of “noisy” bumpiness, and very little if any specular highlights, and is the right color under your lighting conditions, it’s probably going to be perfectly believable … unless you’re making a training video for a plastics extrusion company.
Be sure to take the time to bevel all of the edges of your model.
Also, one simple trick is to provide the viewer with a nice, juicy close-up shot early on, where you use a “nice, juicy texture” like cgslav’s masterpiece above. Thereafter, you can switch to simpler, faster textures which are of the same color, and the viewer will “see” remembered detail that isn’t actually there.