We have the most success with 2.5% hydrocortisone cream.  It’s prescription strength (prescribed by her dermatologist), and it works immediately.  Then, we can hold it off for a few days by using Eucerin lotion (the super, super thick kind), and it slowly returns.  We can usually go a week or two before we have to use the prescription cream again.

FWIW, DD’s eczema is far better when we keep long t-shirts and long pants on her.  I know it’s counter-intuitive in the summer months (and a lot of her issues are skin allergies), but we’ve had success with it.  We just put her in light leggings and a thin shirt (the ON ones are awesome for this).