my aim now is to react quicker with the throttle cut
I suspect that a rapid throttle chop will see most of your problem evaporate - it really sounds to me like you are finding things a bit too busy and just need to be able to sort it out in your own hand-eye universe. Keep in mind that, for a low speed cut, runway distance isn't going to be a major problem so don't fuss too much about hooking into the reverse - if you get on top of things quickly, you will be stopped by the time you get into idle reverse. Hopefully your training setup will allow for some practice runs - it is amazing just how quickly skill follows a bit of confidence building no hazard practice.
I very fondly recall an upgrade captain (744 to 732) who had never really got on top of engine failures as an F/O and had a real confidence problem. His intake buddy, likewise, was having considerable difficulty as well. What to do ? Easy, we needed to fix the problem there and then to make it go away. So, we organised a spare fun session (which had a spare session following which allowed us to run past the normal 4 hours - we ended up doing about 6 hours) in the box and really got into the failures and OEI approach and landing stuff. One of the best ways to maximise exposure is to exploit the freeze and reset capabilities (to minimise time wasting) and alternate LH and RH the whole time to keep fatigue under control. At the start of the session they were really having troubles with very simple failures. By the end, min V1 0/0 seizures (reject or continue - and that box put on a good shake, rattle and roll dance for the continued takeoff from min V1) were a doddle as were ILS recoveries 0/0 to a full stop. All done mandraulically, raw data, hand flown, single pilot by the end.
At the end, (and they were getting a bit knackered by then) I just said "I can't make it any harder for you, chaps, let's call it a day". Well, these two guys, dripping wet with sweat, clambered out of their seats with the biggest grins on their faces you could possibly imagine and swelled heads the size of watermelons. OEI presented no problems at all from that point. In fact, the operator checkie who did their final endorsement check confided in me afterwards that he really was expecting to see the upgrade fellow fail on his handling, based on his F/O history. Very satisfying for me as an instructor.
not in the Challenger 350 FSI sim
I have no experience in that particular box so I accept your comments. I did have some time in a Challenger box, years ago, and thought it a very nice little aeroplane. However, we didn't get into really critical OEI stuff. 5 deg roll limit ? - how ever do you handle a decent crosswind landing ?