I don't think that isopropyl strips the shine. Rather, it just spreads the flux around in a sticky thin layer. What helped me on SMDs is using denatured alcohol and single passes with a /NEW/ toothbrush. Toothbrushes pick up the flux fast and have it stick, which then gets spread around if you keep using it.
For TH soldering, I use rolled up paper soaked with alcohol, and then just shred it over the board. Another option is if you have a lot of the alcohol, just pour it into a container, and leave the pcb in there for half an hour or so, shaking occasionally.