Two Live-ball Penalties
 

NFHS...
Kick Off run back for TD, Returner begins celebrating at the 10 YD Line on his way in with a big raise fist pump... On the return Kicking team commits a personal foul at their 30 Yard Line.

Two fouls: Unsportsmanlike and (PF)Personal foul...

Scoring team(receiving team) could decline the PF.

How do you administer:

Not a football official, but did NFHS also change the penalty for unsportsmanlike taunting to a live ball call? If so then you would have offsetting penalties and replay the down I would imagine.

If the rule is still "all unsportsmanlike penalties are treated as dead ball penalties" then you have a live ball penalty on the kicking team, which is declined, then a dead ball unsportsmanlike penalty on the offense after the score, so it would be penalized according to the rules for such a penalty.

Unsportsmanlike fouls are always enforced from the succeeding spot and do not create a double foul when they occur during a live ball. This is not a double foul.

R may choose enforcement of K's personal foul on the try or subsequent kickoff, and K has the same options for R's unsportsmanlike foul.

A big raise fist pump better be really blatant or directed at the stands or an opponent before you start flagging that as USC.

Agreed, that does not sound like a foul. But that is an aside. As the others have said, you do not have a double foul here since USC in this case is a live ball foul treated as a dead ball foul.