English Translation
He bathed and dressed.
We don’t usually translate ”to dress" as 正装する. 正装する strictly means “to dress properly in a very formal attire” such as a tuxedo, an evening dress or an expensive Kimono.
If you simply mean “to put clothes on”,
彼は入浴して着替えた。（きがえた）
彼は入浴して身支度した。（みじたくした）
are the standard expressions.
The first sentence literally means “to change clothes”, which is a common action after taking a bath. But the problem is that it may also mean he changed his clothes to a pajama to go to bed.
The second sentence is better translation for “dress” in English. 身支度 consists of 身 = body/social status, and 支度 = preparation. So, 身支度する as a verb means “to get dressed to meet someone”. It doesn’t necessarily mean “to dress in a fabulous attire” as 正装する implies.