My 2 cents:
I'd suggest that you try not to scuff up a ball just before bowling at the lanes. Try to keep an arsenal of balls (like 3-4 to a league and 6-8 to a tournament); this helps because you know or should be aware of what grit each ball has, so you know just what to use when you need to adjust. When you touch up a ball just before bowling, maybe because of what you see, it's handy and convenient but what grit are you now using? Can you replicate that surface when you need it again next time? Probably not.
Also, as 10-ITP indicates, dull balls tend to migrate to around 600 grit after a while, but that generally does not happen in 3 or 6 games. Dull balls are also affected by oil much more rapidly than polished or pearls. Using a item like Doc's Elixir (see past posts in this Forum; great stuff) will help you keep your dull balls (especially) from being adversely affected by oil and absorbing the oil. It also allows you to wipe the oil off extremely easily. If you use dull balls a lot, you MUST try Doc's Elixir. A good towel will help a lot also. You can use Hook-it on the ball, while having the Elixir on the ball at the same time, according to Doc.
For me, as far as my experience goes -
Without the Elixir, rolling a dull ball over oil, frame after frame will build a oil shine on the ball and potentially reduce its power and hook. The effect will depend on the amount of oil and how dull the ball is and how quickly it absorbs the oil.
With today's oils, I have to believe that when using dull balls of any type, you must not only wipe off the ball after every frame, but you also have to do at least a quick clean after each tournament or league use. This will help maintain its reaction and increase the usable life of the ball, protecting your investment and your scoring ability.