Hi Dizzy. Sorry to hear you had a hard day.
Sleep training is like any other skill being learned by child or adult, we rarely master something on the first day, it takes practice, but over time you will succeed with it. Shush pat isn't going to be a quick fix if your LO is used to being held for the second part of his nap. APing is a quick fix, independent sleep is a life long skill, it's well worth the time and effort it takes at the beginning.
It would be useful if you could post more info, your EASY and how naps usually take place (ie wind down and AP) so we can see the bigger picture. He could be OT or UT but it's hard to say without seeing your EASY. You can post your 'usual' routine and then also post todays EASY.
With shush pat you can adapt it to suit your LO, it doesn't have to be patting his back if he likes to sleep on his back, it can be a firm hand on the tummy or stroking the tummy or stroking his head if this is what he likes, the main thing is to find something that soothes him and to try to reduce and stop just prior to sleep, do more at the 30 min mark to extend (or set yourself up prior to 30 mins and httj - hold through the jolts - to try to prevent the full wake up). Also some LOs get frustrated with the sound of shush (very young LOs are usually soothed by it but as they get older it can become a distraction from sleep rather than encouraging sleep) if you suspect this is the case you can either be silent or replace shush with a key phrase such as 'it's sleepy time' or 'it's ok you are just going to sleep now' which can be repeated kind of like a meditation.
Unfortunately there can be grumpy times and crying, he is in the habit of being held during sleep and now he is being shown how to sleep a different way so it is understandable that there will be some confusion and resistance, plus if he didn't get his full nap (because you didn't hold him) then he was likely OT the rest of the day which can lead to screaming. If you have an unsuccessful morning nap you need to reduce the next A time and try for another nap to keep OT at bay.