best way to level up to lv 99 by far

first, collect 500,000 gold and buy the Duplicator, then fight Guardians (the armored golden knights in the 2 rooms before you face Dracula. They give an insane amount of EXP when you first get to the Inverted Castle and even up until about level 65. they continue to give you more than 1 experience points until about level 73 or 74 but even once you get past level 65 it starts to take awhile to gain a level. i would say once you reach about level 65-68 go to the Inverted Chapel to the room where you fight the Spectral Sword with all the shields and spears as killing the enemy and all of these gives you 11 EXP in total which can be done very quick in as little as half a second if you position yourself right to the very end of the door and use the Power Of Sire with the Duplicator equipped then turn around and turn around again very quickly to be back in the room with a new Spectral Sword spawned. So basically all you have to do is keep repeating this over and over and when you get to high levels over level 70 you can gain a level in as little to 15-30 minutes depending on how fast you are with it. I reached level 90 in only a few hours of grinding like this but i got too bored to get all the way to 99 but one of these days i will finish it because it will only take me like 3 hours tops to achieve this. has anyone else reached level 99 this way or with another method?