The firing order of a typical in-line four is 1-3-4-2, so add that to your four-stroke sequence and you have the complete order of activities
For a straight six the firing order is something like 1-3-5-6-2-2. A V12 is typically the same as the six, but bank A follows bank B: A1-B1-A3-B3-A5-B5 and so on.
Actually these are BMW firing orders but they are typical of inline engines. For vees (including boxers) it might be different; I would imagine a V8 to fire like two 4-cylinder engines, and a flat-four to fire like two 2-cylinder engines.