Below is the design process I use for such client work.
I always begin with Clip Studio Paint to create sketch work as it allows me to produce quick rough grayscale sketches that can be used to exchange ideas with the client. Below is the origins of The Bearfuls.
Using the sketches I create a rough colour guide to get an idea of how the final product should look. Dead Jam and I gave them colours to match their personalities.
For Bearfuls Adobe Illustrator was then used to create the final pieces. I also use Photoshop or Clip Studio Paint depending on the piece and usage.
The Bearfuls sticker pack is currently 50% off and avalible on the iOS App Store.
To celebrate the stickers launch here is a code for 1 lucky person to redeem on the app store: M997Y37T7WPW