Holding priority, cast Reiterate with buyback by paying ({4} magic symbol) ({R} magic symbol) ({R} magic symbol) , copying Explosive Welcome twice and returning Reiterate to your hand.
Resolve an Explosive Welcome copy, dealing 5 damage to any target and 3 damage to any other target, and adding ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) .
Repeat step 3 for the other Explosive Welcome copy.
Repeat from step 2.
NOTE: Because Explosive Welcome requires two separate targets, you may need to target yourself if you are down to one opponent and they control no other applicable targets. It is best to ensure you control creature(s) to target with the damage, or that you have a high enough life total to sustain it.