I recommend a small blush brush.

This is Innisfree's mini blush brush. I measured it, and it is 11.5 centimeters. The reason I bought this product was for portability. Large, long, and full regular brushes are a bit cumbersome to carry around, aren't they? There are actually many small products available. The reason I recommend this one is that brushes that are too small aren't ideal. Also, I don't like brushes that are too flat; they make it difficult to apply the product naturally and subtly. This brush is small and portable, yet it doesn't feel sparse. If you use blush frequently, I think it would be good to have a product like this on hand at home.