Nick's right. This isn't an exact type of thing especially cause there's several factors at play here that we cannot predict without actually doing it. E.g. the new med might not work at all or otherwise not as expected for various reasons that we can't predict until it's done. E.g. the Latuda binds different receptors and differentials not the same with Thorazine, the patient's metabolism of the meds etc.
The only medication coming to mind where you can easily cross-titrate in a very predictable manner is Escitalopram to Citalopram because the active medication is the same exact thing.
Even when converting an IR med to an ER med of the otherwise same exact med problems could occur. E.g. Adderall ER to IR the patient might c/o of a "crashing feeling," or when doing IR to ER they might state they feel the effect longer but it's never strong enough to treat their problem.
In outpatient, for psychosis, I cross-taper very very slowly. E.g. like up to 20% of the medication dosage a month at the fastest. Reason why is cause if it won't work well you'll be able to catch it before things get real real bad (e.g. full decompensation requiring hospitalization). If inpatient, I might do it faster. E.g. up to 20% change of dosage every 1-5 days.