Try thinking one-lol-ly, two lol-ly, three lol-ly. Try listening to some 9/8 songs by good musicians and fitting this pattern to the pieces before you play your mandola, so that you get used to it.

If you are doing accompaniment, try saying to yourself (for instance) D-lol-ly, G-lol-ly, D-lol-ly as you fit the chords to the tune.

This applies to tunes which are all eighth notes, of course. Most fast dance tunes are mostly eighth notes.