I'll have a go at this and use Durandal my male Dratini. I assume I attack first ( I would anyway...sending and attacking first? o_O) Now then...
Durandal, start off with a nice Double Team. Then, if Squirtle tries to attack and hits a clone, follow up with Thunder Wave. If it hits you, counter with a Thunderbolt. Then, use Thunderbolt or Thunder Wave , whichever you didn't use last round.
Double Team ~ Thunder Wave/Thunderbolt ~ Thunderbolt/Thunder Wave.