Hi there

I came to the same decision a while back, brf only have a limited amount of food.

We try to use pure rye berries for cakes, 24 hr soak and boiled till they split, then towel dried, topped with dry verm, then pressure cooked.. The yields are greatly improved over brf.

Thai rye cakes

Cambodian rye cake

But if you haven't got a pc you can do BRF cakes but when they area 100% colonized and ready to birth, you can use them as spawn instead, Just crumble them to a bulk substrate (thanks to Jamie)

Common bulk substrates are :

Horse poo

Coir

straw

hey

Ideally you could use pasteurized hpoo, but coir works well, as does straw and hey, you can mix and match, make sure you add some gypsum... So you prepare a tray, then crumble your cakes into it with your pasteurized substrate, mix well or layer, cover with plastic and make holes, keep at 82f ideally, then it will be ready to fruit in like 7 - 10 days.

I Do a similar thing with rye, but I don't do this using BRF, but this technique is one way to be able to do bulk grows without the need for a PC

Hope this helps

Peace