It really depends on where you work and how that work takes place.
In my experience, the best tools I had were always scrap books, pencils and markers. As an exhibit designer there will be a time where you are a salesperson and youre pitching an idea. You supplement that idea with visual media and you try to communicate the feel and look of an imagined space.
There really is something special and warm about hand drawn designs. They don't have to be photo realistic and they don't have to be spatially accurate. I use scrap books with pages that act as broad identity concepts and other pages that are individual identity concepts for specific walls, displays or sections.Its literally swatches of color with printed or cut out images pasted in to give an impression of whats to be.
Don't forget the value of scale models. A lot of people are just not sold on seeing stuff only on a screen. Being able to physically hold it and move around it really inspires confidence and connection.
However I always pair this with a 3D render. My preferred program is Blender because I'm more comfortable with it and I feel as thought I have more control in creating a warmer or more emotionally persuasive render than SketchUp. Blender is a beast and the learning curve is rough, but the results are stellar.
SketchUp, however, is king for planning designs that are to be built. I find it super easy to build furniture, displays and gallery install plans in SketchUP. Its a lot easier to quickly lay out stuff to specific dimensions and distance in SketchUp than on Blender and I can even export files to cnc cut for flat pack furniture and displays.
Hope this helps!