Do the arithmetic before deciding anything, because "does not scale" is usually a feeling rather than a number.
Twenty hours a week producing — what, one customer a fortnight? Work out your actual cost per customer in hours, then compare against what a working scalable channel would cost you. Content takes months to produce anything and often produces nothing. Ads cost money you may not have and need a message you have already validated.
When people run this they usually find the manual channel is not merely acceptable, it is the best-performing thing available to them by a distance, and the discomfort is social rather than economic — it feels like it should not count.
The number that would actually change my answer is how many good prospects are left. Twenty a week is sustainable if there are thousands of them. If your total addressable set is four hundred people and you have contacted a hundred and eighty, you have about nine weeks left and you should be building the next thing now. That is the calculation to run, and it is the one nobody does.
So: count the pond before you worry about the fishing method.