When it comes to applying foundation to blemish-prone skin, try and establish what your main skin concern is. Opting for a powder formula with a rich, creamy texture will help disguise any bumps or unevenness while staying put all day. If you’re more concerned with a uniform finish - for example, to disguise patches of scarring or redness - consider using a brush to apply evenly across the face, taking care to blend out around the temples and jawline.
Skin that’s prone to acne tends to suffer from excessive oil production, which can result in skin appearing visibly shiny or greasy. Applying your foundation with a sponge will help the product penetrate the skin for an even, matte-look finish. If you prefer to use your fingers to blend out those hard-to-reach areas, make sure your hands are clean to avoid spreading bacteria or irritating existing blemishes.
Sources:
[1] https://www.aad.org/media/stats-numbers
https://www.nuskin.com/en_US/corporate/company/science/personal_care_science/acne.html
[2] Hayashi N, Imori M, Yanagisawa M, Seto Y, Nagata O, Kawashima M., ‘Make-up improves the quality of life of acne patients without aggravating acne eruptions during treatments’, in Eur J Dermatol. 2005 Jul-Aug; 15(4), pp. 284-7.