Tips and tricks I've figured out from playing the single player. Actively updating as of September 2020.

Each shrine head has a counter.

You can complete shrine heads by going to survival mode, finishing the 1 round with a fatality. When the tower ladder loads again to show your advancement and your next kontestant, escape out to "Tower Select".

Repeat the tower to re-grind the same 1st kontestant's head.

You can use AI battle (many guides on what bot settings to use, a kommon one is 30 kombo 30 reversal), rubber band your confirm button (A on controller), or manually hit kontinue to advance.

If you have the right soul augments though you can do the following:

To grind koin (not that you really need to):

1. Put in the soul/heart konversion to koin augments
2. Put in "no damage krushing blow" augment.
3. Put in selfless mercy augment.
4. Put in hearts for mercies augment. Put in souls for krushing blows augment.
5. In a kombat (like survivor mode), use "no krushing blow requirement" konsumable, spam mercies/krushing blows until you're bored, hearts and souls will be konverted at some insane ratio, depending on the level of your augment.

Remove the konversion augments if you want to farm actual souls/hearts.

A lot of guides suggest farming Reptile for 200 at a time, but it takes forever to search for him in the krypt. With the augment combo above you can get 200 in about 5 minutes.