I'm Irish by birth but have lived in Scotland for 49 years. At age 12, after 4 years in Glasgow, I had more or less mastered the Scots accent. The pronunciation of "r" however gave me away for a long time. I'd say that the Scots "roll" it: "trill" is also a fair description, eg, the "R-r-r-r-r-r-rolling Hills of the Borders". "loch" is also a tricky one, never say "lock"! OK! Having said that, even some Scots kids are now, under the influence of English tv, saying "Lock" Lomond. Incidentally, I can now roll my r's with the best of them!

As for singing the songs, I'd suggest that you sing any song any way that you want, and the deil tak the hindmost. I love Dylan singing "Arthur McBride", or, "Arthur McBryade", as Bob would have it!