Have you guys seen this Kickstarter?https://www.kickstarter.com/projects/le-glue/le-glue-the-water-soluble-adhesive-for-lego-blocks
I was the first to jump in! He's since added a level where you can get 6 pots of this block adhesive. I'm not affiliated. Just excited. Lee, Tripp's dad emailed me to let me know that it is thin enough to use with a brush. You may see a picture in the Kickstarter media that shows Tripp dipping the block. It's not that messy.
I love the back story
"How it began
Thank you for viewing my project. My name is Tripp Phillips. As an aspiring inventor I started building with LEGO® blocks as far back as I can remember. Building blocks allowed me to be creative and make all kinds of silly contraptions (like inspector gadget). The only problem was my stuff always fell apart. The coolest of spaceships, moon landers, you name it, I built it. They looked really great, but I couldn’t play with them; wings would fall off, wheels rolled away, it simply drove me nuts. Super Glue or Krazy Glue® wasn’t an option as it ruined my bricks forever and bricks aren’t cheap. This was the problem of every kid in the world (and adult kids too.) I was determined to figure out a solution to overcome this problem and stop those messy breakups. My invention, Le-Glue® is the answer."