My first children's book came out in the winter of 2011, so I've been doing this professionally for about five years now. I have always drawn and written in one form or another and have found children's books to be the perfect intersection of those talents. It also help to have the creative mind of an eight year old.
2) How many books do you have out?
As of this writing I have sixty-nine unique titles (there were some anthologies created.) This equals out to a little over ten titles per year. My pace has slowed down significantly as my focus has shifted to doing detail oriented illustrations and complex narratives.
I can't say that any of them are more challenging than the others, however, each one has a challenge in relation to the demands of that audience. What I have found is that reading level is fluid for children. Some children read beyond their level while others prefer easier titles. I've met six year old readers who are almost on young adult and I've read to a class of sixth graders that preferred picture books. The true difficulty in all this is communicating what grade level you intended to read the book when you made it. That's something I still haven't mastered.
Sure, there are two main techniques I use to make the pictures. One is to do a completely digital process that uses a combination of Manga Studio Pro and Adobe Photoshop to create the images. There's a video of this process for "Nuts" you can watch here. The drawing is done with the help of a Wacom Intuous tablet which allows for natural pencil movements. The other method uses pencil sketches which are then scanned into Photoshop and colored. This is done mostly for speed, as the computer programs cannot do any of the work for you (there's also the added perk of being able to undo mistakes.) Coloring in Photoshop involves a lot of layering and "pushing" of color in order to get rid of the digital feel and make it look organic.
My stories are intended to teach imagination and heart to children. They cover a wide set of topics, characters, and tones, but the main themes always involve understanding other people and including them. Beyond that, I just hope that the children are entertained and that they have shared a special moment with their parents.