Persevere, Les. 9/8 (and 3/2 even more so) are both slightly archaic dance and song rhythms, so you won't have them drilled into your bones from a lifetimes top twenty(or whatever)listening.But they'll soon come naturally once youve played a few tunes.
   The Rocky Road to Dublin is a slightly different rhythm to Drops of Brandy and the Fox Hunters, which is probably why its not coming so easy. I dont think there is any agreed terminology for the difference. With 6/8 jigs, the distinction can be made into normal(or double)jigs, and slides(or single jigs). The basic difference is the double jig is sort diddley diddley , but the slide is more tumti tumti. In the case of 9/8 tunes, the Drops of Brandy/Fox Hunter tunes are more diddley diddley didddley, and Rocky Road to Dublin is more tumti tumti tumti.
    The direction you move your pick in will take some while to settle down...different players use different approaches, so you cant really say what's right. I play virtually all the main beats on a down stroke, in jigs and slip jigs, but not everybody does that.