I'm not sure, given their mutual impatience, that they wouldn't just rush in anyway. Damian could throw some bombs/gas/etc at him, but he's kind of arrogant, he may just try to take him on in H2H right off the bat. In which case he'll find he's at a disadvantage.
A lot of people seem to forget that rushing into battle without thinking is something Damian only did when he was beginning as Robin in the old continuity. He quickly learned to be more cunning. A good example of this is an issue of Superman/Batman in which he allows himself to be captured by Killer Croc, just to get a good opportunity to catch him off guard. More recently he has been depicted as someone who fights quite tactical when facing stonger opponents. Even before Batman trained him he took on Man-Bats enhanced with Venom and won ( Batman and Robin #0). In the second Batman and Robin Annual Bruce learns that Damian managed to defeat Tusk, a super strong villain that gave him quite a beating during his first fight with him (, sadly its not shown how he did it). And in Secret Origins #4 he was again shown battling Killer Croc, and this time defeated him only using a taser.
If Damian is outclassed in close combat or can´t take out Raphael with explosives and batarangs he´ll change his tactic. Perhaps he will use the fact that he is a kid to get the Ninja Turtle to drop his guard, which would give Damian an opportunity to use knock out gas or the technique he learned from Nobody in Batman and Robin.