Step by step: you could not expect your kids to learn at the same time to put all kid clothes. You should structure the task at different stages, depending on their level of difficulty. During the first few weeks, you can leave that you only underwear and socks, gradually introduce new elements.
No end for him: delay before the children to wear, it is common for parents to be who end up placing most small kid clothing. Thus, children lose the motivation to perform the task of dressing themselves and take long to learn to put some best baby clothes well.
Give them time: To strengthen their skills, it is normal to be slower. At the beginning of learning to put on baby clothes, it is best to choose times when you have no hurry (and weekends) and, later, restructure and raise the child hours earlier so that time is not a discordant element.