First of all have 3 save slots. Go up to your 1st of 4 columns in the haunted mansion and save in slot 1. reload as usual until you get your first scroll. The more types of scroll you collect the better your chances. Now lets say you get a Lloyds Beacon scroll, you now save in slot 2 See if you get a second scroll and if you do then save it to slot 3 If you don't then reload at leat 3 times just to make sure its a dud save then go back to slot 1 and try again. Now i know you don't want to lose that Lloyds Beacon but if you accept it at this point thats all you are getting from that one column. Keep saving in a different slot when you get something you want and going back to the previous save if you don't get a further scroll. On average it will work every 3rd time and occasionally you will get a really good run of three or four in a row.

Using this method you can "multi-loot" a single column until you are bored and want to do something else then come back to that column at a later time. Believe me you can get all you want from that column. There is no limit to how many scrolls it gives using this method. In fact there is no advantage in ending one column to go to the next since your chances o a further scroll are the same after 100 scrolls as they are after the very first.

Obviously the school of sorcery is stil usefull if you need to get say 4 scrolls whith much less reloading time, but after those first 4 scrolls you have have to apply the same principle to multi-loot.