Adding CYA or not

[resurfacing confused]

I just resurfaced my gunite pool with Fiberglass. I'm using trichlor tablets in a floater for my daily chlorine needs.

When the water was first tested there was no Calicium and I added 25lbs of clcium hardness to my 20,000 gallon pool. The store told me after I got the alkalinity ideal and the ph to shock with Calcium Hypochlrite whic hovertime would build up my Calcium level.

I was going to add CYA but I'm wondering if I use the trichlor tablets can I just wait for the CYA level to increse. I'm sort of thinking this is similiar to what the pool store told me in relationship to the Calcium. That is by shocking with Calcium Hypochlorite I would be gradually raising the Calium Hardness over time. Does the same theory make sense for my getting the CYA level between 30 - 50?