You might try what my piano teacher calls slow motion practice.

Practice in rhythms. Dotted eighth/sixteenth and vice versa keeping in mind the relaxed feeling in your fingering hand. This allows you to play two notes 'a tempo' while keeping the relaxed hand position. You are practicing in small chunks and yet still going fast.

When you are able to do that, divide the notes into groups of threes (for jigs) or fours playing one slow note and following it with two or three fast ones.

I should add that this technique can improve anyone's playing no matter the instrument. If you want to play fast, you've got to learn how to play slow!!