how much would you use, cast perlite and soilThats a bit heavy on the casts, did a successful grower reccomend that?
Yes you can use worm casts all through flower.
Indoors I put some in hole at transplant. Top dress every two weeks during veg and flower and my teas are primarily worm cast based too.
Perlite and soil you got to figure out for your needs. Add perlite to wetted soil lil bit till it meets your needs. But you shouldn't need 25% perlite added.
In a 5 gallon pot I put 3-4 ozs casts in hole at transplant. Then top dress same amount and water it in. You can go heavier with casts but 25% is too much to mix in soil IMO. Ive seen failure with planting in 50% and 100% worm cast experiments.