I am not able to find any documentation or examples on how to add McAfee Anti-Virus to VMs/BMs at the provisioning time via SL Rest or python API. Is it possible to do it at the provisioning time? If not, how to alter the device after creation to include it? Could someone please provide examples either way please?
It is possible but you need to use the placeOrder method, the method has as parameter a list of prices these prices represent all the items that you want that your device contains. however the method is not so easy to use because you need to pick the correct prices.
As you are using the Python client I recomend you to read this article:
http://sldn.softlayer.com/blog/bpotter/going-further-softlayer-api-python-client-part-3
Also you need keep in mind that you cannot pick any price for any location, the prices are differents for a particular location, if you pick a price which is not valid for a particular location your order will fail. However Softlayer provides a standard price which work for any location, this standard price is converted to its equivalent price for a particular location, so you could use that prices in order to avoid issues with the locations. I recomend you to read this article about that:
http://sldn.softlayer.com/blog/cmporter/location-based-pricing-and-you