I load a lot and almost all of it is with my own cast bullets. My 223 reloads are the only exception. I also cast bullets (tumble lube for 45 acp and PC for 44 mag) for a shooting buddy.
You do need lube but you may get by with the easy option, tumble lube. Lee lube is a common product but it leaves the bullets pretty sticky. There is a small time guy at White Label Lube that has a better product, 45-45-10 (
https://lsstuff.com/store/index.php?main_page=product_info&products_id=13). I use tumble lube for mild loads, think 38 special, 32 Long.
Traditional lube is normally applied with a lube sizer. It can be applied other ways, but few bother. For many applications, traditional lube will handle higher power loads than tumble lube. Getting leading free medium to higher power loads with traditional lube can require getting everything (bullet alloy, bullet diameter, case prep, etc) just right. Even still, some guns just seem hard to please with traditional lube. If you do want to try traditional lube, the products at White Label Lube are considered great choices.
Powder coat (PC) is the new kid on the block. I use the ASBB tumble method and hand stack for cooking. I use this for my 9 mm loads, my magnum pistol loads, my 357 Max loads, my 357AR loads and my specialty pistol (7 TCU, 30 Herrett, etc) loads (all full power). The lube performance with most of my PC loads have been great with no fiddling around at all. The 9mm loads were the exception. It took lots of work to get leading free 9mm loads.
Many have pretty good luck right off the bat with cast subs in the 300 BO. I would not hesitate to try any of the above for 300 BO subs. Again, the 9mm can be a problem child. You can try any lube you want with the 9mm, but consider yourself lucky if you get happy without a lot of effort.