Tikka223,
I'm thinking the Harbour Fright unit might be a large part of your problem. There are different degrees of power, obviously. Wattage may be pretty low.
I'm using the Hornady 2L cleaner with 1.5 litres of fresh water, 3-4 ml (short teaspoon) of Lemishine detergent booster, and a tiny squirt of Dawn dish liquid. Hornady says not to use the cleaner without the plastic basket.
I use the heat cycle on the cleaner for probably 15 minutes, enough to warm the liquid. Hot tap water would be the same effect probably. I'm using softened water from a reverse osmosis system, so it's pretty clean.
4 or 5 times fired brass (not cleaned internally at all in it's life) is coming fairly clean internally in 30-40 minutes. Once fired brass is really clean internally. I clean the primer pockets with a brush first, that's stubborn stuff.
As to how much effect it has on velocity, my reloads in a 6.5 Creedmoor went from 2865 fps average with non-cleaned 4x and 5x fired brass, to 2850 fps average with cleaned brass. Over that number of firings, it's a minimal difference in my case. Carbon buildup does have an effect on case volume.