What you're talking about, then, is not just an accent or an occasional dialect word, but something that is arguably a different language from English.

The trouble with full-blown Scots is that English-speakers have the feeling they ought to understand it, and get irritated when they can't(this happens to genuine Scots singing in Scots too, although some of them quite enjoy getting up the noses of the English!). This doesn't apply to French or German, which the audience either understand or don't, but somehow Scots goes down less well, particularly if the listeners sense or know that this language is not coming naturally to you.

Scots speakers will spot the fakery right away, and also get irritated by it.

Sorry to be so negative, but I can't really think of a solution!

Marje