Just treat like any other horse who has ulcers. A course of Gastro Guard (or similar - Ulcer Gold etc), review management/ feed. Ensure horse has eaten some chaff/ hay in the 30 mins prior to work to reduce the risk of acid splash and try to keep stress to a minimum.
I would hope they are not 'in pain/ distress' and if ulcers were suspected they are scoped and treated, I think more trainers are aware of the issue and routinely scope/ treat, certainly the trainer local to me has his scoped routinely now and treated as required, he also put new arrivals on a course of GG at one time, not sure if he still does but it shows his attention to detail which is why he is so successful.
Prevention is better than cure but you need to know where you are starting, if the horse is in pain it needs to be investigated/ treated and then managed.