So lets say you just transfered proteins over to a nitrocellulose membrane (or some other type) and now you need to non-specifically block the rest of the membrane but you don’t want to buy anything expensive.
Try using nonfat dry milk.
It is likely that any lab performing western blots already knows about using nonfat dry milk to block their membranes but it is nevertheless a great way to conduct blots on the cheap. Just mosey on down to the nearest grocery store and pick some up for a couple bucks.
5% nonfat dry milk in PBS will work for some gels.