Waterproof Chairs

I am sealing two chairs outdoors. I leave the bare wood and using multi-surface waterproofing Thompsons. They are out for sanding and I want to know if it is better to apply the seals before putting them back together? Is it important? Is he going to last longer? Etc.

Hello,
You better

Since you have the chairs outside, it will be easier to apply the sealing of all sides of each piece rather than putting it back together and then seal.