Scrubs & masks
As oily skin produces too much sebum, scrubs and other exfoliating products can be useful in preventing blocked pores, which could lead to problems with spots. Because they deep-clean the pores, they also offer the advantage of refining skin texture and brightening the complexion - often dull in people with oily or combination skin. Always rinse with cold water, as it tightens the pores.
Recipes for clay and charcoal masks, which are known to absorb excess sebum, can be found on the internet. Be careful, however - some people's skin is sensitive to these ingredients and reacts badly to them, as the quantities indicated can be somewhat random. You also see a lot of traditional recipes to combat shiny skin, based on plants with astringent properties like hamamelis and lemon. Once again, be careful - their effect on oily skin is not clear and there is a chance of sensitisation.
Similarly, the jury is still out on whether it’s a good idea to use cleansing brushes on oily skin. Many dermatologists feel that they strip the skin too much and alter the hydrolipidic film. For combination skin, you can use two kinds of mask alternately, one to purify and one to moisturise, applying them to the oily or dry areas respectively.