I have found a few tricks over the past few years that help me keep things simple as well as cut down on wasting time in the classroom. My elementary classes are 30 minutes back to back so I don't have any time to waste!
Often I will have my supplies cut and set out the night before. I am coming to the elementary right from the high school, so I don't always have time to prep things when I get there! So before I leave I try to make sure water cups are full, paint brushes are already divvied out, and all that good stuff. In this case, my first graders were painting lines with pieces of cardboard. So I cut the pieces, set 4 of them each on 6 paper plates (one per table, four students at each table) so all I had to do when I walked through the door was poor the paint!
This is something I LOVE LOVE LOVE. I learned this from a teacher I observed while student teaching. I have a bucket that I fill half full with warm water and put in a little dish soap. Then I soak sponges in the water while students are working with paint/watercolors/markers/anything that can get messy. Once the students have put away their materials at the end of class, I can quickly pass one sponge per student (or one per two students to share) and they can then wipe their fingers off if they are dirty and scrub anything on the table as needed! They then push in their chairs, bring me their sponge at the door, and line up. QUICK AND EASY! No lines at the sink, no wasted paper towels, no extra fuss on cleaning the tables. It's awesome. Once the sponges are used I wash them out and line them up on paper towels to dry out over night. I will change sponges a few times over the year because of course they will get pretty dirty.
When students are painting or using messy materials, the tables need covered! I used to waste so much time laying out TONS of pieces of newspaper, that ended up being pushed all over the place. So I decided to use some of the paper from the long rolls of bulletin board supply! I cut two pieces per table, lay them out, and once the students are done either I or the students can quickly place one piece on top of the other, fold it once in half, and fold it again. I store them under a supply table at the back of my room so when I need them all I have to do is place them on the table groups and easily unfold them to cover the tables again! It is so quick! I try to use the same pieces multiple times so that I'm not wasting paper. They might last me 5 or 6 times...It just depends on how messy the material is that the kids are using.