As a former sim instructor at a regional, the biggest skills I saw lacking in new hires were basic attitude instrument flying especially on one engine.

One of the maneuvers you will be required to demonstrate throughout training and on the type ride is a hand flown single-engine ILS down to minimums. This was the #1 failed maneuver I saw. #2 was V1 cut, and #3 was single-engine go-around. Applicants failed these maneuvers for much the same reason: lack of proficiency at hand flying on instruments with an engine out.

Practice hand flying on one engine. Climbs, descents, turns. Practice speed and configuration changes. Anything that gets you moving those thrust levers around and requires you to maintain aircraft control and coordination will be helpful.