A 30-year-old woman with an 11-year history of asthma has experienced recurrent attacks over the past year, particularly at midnight or early morning, and more frequently during spring and the rainy season. Physical examination: generally stable, coherent history without dyspnea, scattered wheezes in both lungs. According to asthma management guidelines, what is the preferred route of administration for corticosteroids and β<sub>2</sub>-agonists in asthma treatment?