Sorry it took so long to respond, quest. I'll admit straight out that I'm not too swift at finding good stuff on the internet. Merytre-Hatshepsut is much better at that than I. I did a Yahoo search under "Ptolemaic burial practices" and "Greco-Roman burial masks" and came up with all sorts of links, and wasn't really impressed with any of them--too short on detail. You get the occasional interesting site like this one,
but all in all I wasn't intrigued enough to continue the search.
I'm much more of a book man. There's nothing like the feel of a book in one's hands. Plus, I like to write notes in the margins, and I fear my monitor would fill up too quickly were I to do that to my computer!
Three books that have taught me a great deal are:
Death and the Afterlife in Ancient Egypt,
by John Taylor
Death and Burial in Ancient Egypt,
by Salima Ikram
The Mummy in Ancient Egypt,
by Aidan Dodson and Salima Ikram
These should all be available at Amazon. The last is particularly comprehensive and also fairly expensive, but well worth it. I'm becoming a fan of Salima Ikram, a very intelligent Egyptian Egyptologist who's one of the up-and-comers in her field.
My favorite area of study happens to be death and burial, but I admit I'm not too knowledgeable about burial practices in the Greco-Roman Period. Some Egyptologists consider this time period a separate area of study, more in the Classical era than ancient. The Greeks and Romans had profound influences on the Egyptians, and especially in Roman times we see a degradation in the essence of Egyptian-style burials. Egyptian motifs and symbolism are still used, of course, but they are increasingly less understood and are mixed in with Hellenistic motifs.
An interesting thing about the portrait mummies of the 2nd and 3rd centeries CE is that they often were not immediately buried. It is thought they remained in the homes of the families for a time, in the manner of Roman ancestor worship. Wear and tear on these mummies, as well as the weakening of the bandages in the ankle areas, suggest these mummies were propped up. Cupboards have been found with double-doors that are believed to have been the containers in which these bodies were stored in the home. You could prop open the top door to view the portrait and provide offerings or ask advice of the beloved dead. At a later time groups of mummies were taken together for common, mass burials in the crowded necropoli.
I'll stop there before I bore you too, much, quest. Sorry I couldn't be more helpful. Maybe Merytre-Hatshepsut could point you in the direction of some interesting websites I missed.