I am a farm girl, married to my high school sweetheart. We grew up on farms 9 miles apart and went through 12 years of school together. I liked him in grade school, but it took until we were Juniors in high school to get him interested in me as more than a friend. I have never lived more than 10 miles from home, except in college, but have travelled as far as France, Germany and Switzerland. We live on our own farm and have raised three of our six kids. The last three are growing up fast.
The older Bible School kids made these popular crayon drip canvases on the day we had the rainbow theme.
When I do this in groups, I let the kids arrange their colors to their heart's content. When they have them all set, we run a strip of painter's tape across them to hold them in order. Then we carry the canvas and colors to the hot glue station (manned by adult) and flip the colors off to the side. (See below.)
The glue-er quickly squirts on a good amount of glue and then we quickly flip the row of colors back and push it into place on the hot glue. After a second, tap each color quickly to see if they are stuck on well. Hold colors down while gently removing tape. Re-glue loose colors. Done!
I try to have several glue guns going. Some work better than others. I recommend a test run with each gun before you start with a group. Some glue does not stick as well as others.
I've learned that the melting process also takes multiple blow dryers. Again, some work better than others. Better to have too many than not enough, Sometimes, the blow dryers overheat and turn themselves off. Good to have back-up! The melted wax is going to splatter, so choose your melting location well. I like to drape the areas we use with plastic dollar store tablecloths to reduce the amount of waxy scraping and scrubbing needed for clean up. Be aware that the table cloths can melt too if the blow dryer hits them too hard. We just poke an out-of-the way hole through the plastic and run the plug in cord through for easy access. We have not had much trouble with wax on clothes, but you might want to assess the age and ability of your students before allowing them to do the melting.
I am surprised with how much creativity can be used in the placement and choice of colors, and even in how much melting is the right amount. The results are always great, and the kids always love this craft.