There are a number of techniques I use to paint high spots such as a roller on a pole, a sprayer with an extension tip, a bucket hung from my extension ladder. Unfortunately, I have never been able to buy an "off the shelf " paint tray that fit on extension ladder. So here is my DIY solution.
Metal paint tray (Gallon size works best)
6 feet of light weight chain. (I used jack chain)
Step 1: Drill Holes in Paint Tray.
Drill small hole in each corner of the tray on deep end along the upper edge. ( you can also use a center punch or nail)
Step 2: Insert 1 Chain Link in Each Hole.
Using your pliers, bend open one link of chain and feed it through the hole you just drilled.
Clamp it shut so it doesn't fall out.
Bend the other end open slightly to form a hook.
Repeat on the other side.
Step 3: Insert Chain Through Rung
Using the remaining chain insert it through a ladder rung 2 rungs higher than where you want the tray to rest.
Step 4: Hang Your Tray.
Slide your paint tray onto your extension ladder. Hook the chain on either side and your good to go.
Step 5: Finished
Finished -ready to paint