That is only part of the question. The full question would be more on the lines of ‘Can anyone work heka, regardless of their spiritual beliefs/religion?’ This of course, leads to even more questions such as: ‘Can I work with other Gods/Entities than the Egyptian ones?’, ‘If not, can I work with the Egyptian ones even if I don’t believe in/worship/know Them?’, ‘Can I substitute things the way I want?’, ‘Can I work heka along with other types of magic?’ and so on.
The answers are long and, in my opinion, quite open to debate and interpretation.
Let’s begin with the first and most important one (which will lead to answering the others too) The short answers is… well, there is no short answer for something like this. Heka is intimately linked to Kemetic beliefs and mythology. Indeed there are whole rituals dedicated to re-enacting and sustaining the Creation. Some of these were done within a temple setting on a daily basis. Others on a seasonal or yearly basis. As such, I don’t see how a ritual designed for the re-enactment (and protection) of the Solar Boat passing through the gates of the Duat for example would be feasible within another set of beliefs. You could change the names of the Gods or Spirits but what would be the point? It would not make sense at all if it’s not within the Kemetic frame. You wouldn’t keep the form nor the substance of it. So you’d end up with an empty ritual.
Not to mention the very occupation of Magician was reserved mostly to priests. In Egyptian thought, heka was not separate from religious and mundane life. Religion, mundane life and heka formed a cohesive and tight-knit frame of life. Heka permeated throughout all of creation. It could not be separated from it and seen as a force just floating about not doing anything. On the contrary, heka (and Heka the God) came before, was a part of and sustained creation and Ma’at.
The Creative act of Heka is not limited to a single event, for in the Egyptian theology the creation is cyclical, being re-enacted with each sunrise. In company with Hu and Sia (‘Perception’), ‘Heka who opens his two eyes that the two lands might see’ takes his place daily on the solar bark of Re, or is seen in prayer, invoking the separation of heaven and earth. In rare instances, he replaces the air god Shu and performs this separation himself. This creative benefaction of Heka by day is balanced by his role as protector of the bark by night. *
The Magician could claim protection by identifying with the Gods, as for example: I am that pure Magician who is in the mouth (or ‘utterance’) and body of Re… On your face, enemy of Re! I am his ba, the Magician.** With words of power such as these, it would hardly make sense to substitute Re with another deity or spirit. Heka places a very high importance on words and their meanings. Perhaps more than other forms of magic. The words one uses in ritual must be clear and have an exact meaning and purpose (and in some cases symbolism). Where words can create or undo and are full of power, one cannot use them as empty vessels. At best, nothing happens and you’re just wasting your breath.
There are of course a few types of rituals/magical techniques which can be adapted outside the Kemetic frame, provided there are similar beliefs/techniques in the frame they are transferred to. For example, one can make a ritual to trample their enemy under the soles of their feet work outside the Kemetic frame. It’s possible. Not easy but possible.
Some rituals and prayers were designed with a specific deity in mind. The way these could be adapted within another frame does not come to my mind. However, when you look at some of the magical texts of the Greco-Roman Egyptian culture, there is clear syncretism of different religious and magical thoughts.
So when it comes to questions such as these, there is a great deal of yes, no, maybe and depends. There is a great deal of personal responsibility involved in working magic of any kind, but I dare say even more with heka. Especially since words can (and do) mean a lot. Gestures as well – since they are a language too (body language).
As for the last one, I personally do. But not at the same time, of course (we don’t want those energies clashing or mingling or goodness knows what!). Or for the same purpose. Let’s take a spiritual healing ritual example. I can work either heka with the help of Sekhmet or I can do a let’s say European folk magic spell. I never work two rituals for the same purpose as a rule of thumb (one I have set for myself). I can work the same thing again at a later time, depending on the results I’m seeking, but never two different workings. With that said, I mostly work heka anyway :)
I realize this topic can spark a debate and I invite you to comment with your thoughts and opinions. And I am aware disagreement can come about but I urge you to keep things civil, thank you!
* R.K. Ritner – The Mechanics of Ancient Egyptian Magical Practice (.pdf edition), pg. 18
**R.K. Ritner – The Mechanics of Ancient Egyptian Magical Practice (.pdf edition), pg. 24