What one can do, another can do. Thrawn's not so good at reprogramming droids, but he is skilled at improvising explosives from power sources.

So once he's away from his previous position, he starts hunting down the ports on the particular droid he's standing next to, physically climbing on the thing if he must, aiming to dig deep into his guts for all the components he needs.

He does not suspect he has a great deal of time for leisure. Somehow.