easire to think of a melody first , orchestrate it and then add on the groove s and rhythms.
also if you were to give a sense of percussive movement... the playing would be more towards staccato.. try to create a motif with the strings and then grace it with beats and textures , apreggiators etc.
in the end it is all bout sitting down.. think of what inspires you and try to write it.
if you use your midi editor properly ,you can make your strings come close enough to the real thing.
imagine how the part is being played and try to resimulate that in midi world.