Arran is a lovely little island. I have familly in brodick and used to go there every summer when i was younger. I never fished on the island, but i'll have to take my rod next time, if there's a chance for a sea trout

As for tacticts, have a look at the sea trout section on here
Orkney Trout Fishing Association Home Page
In general up here, its better to fish the ebb tide and its a good idea to look for a bay with some fresh water running in to it.
A floater or slime line are all you would need, as all the fish ive caught were knee deep or less!!
I use a 10lb leader, about 8 feet in lentgh. Orange seems to be a colour they like very much, so i recommend trying a nicks lure or simillar, heres 1 i had a few on last year.

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Hope this helps
Cheers Thorfinn