Dessicant beads are cheap enough, so is a little pipe. Bake beads about 250-300F to dry and re-use them. Tempature to bake at may vary with type of beads.
I bought 10lbs of the color changing beads, pink/blue, awhile back for I think $20 and shipping.
They were to use for something else back then though.
To build an airline dryer cheap and easy, get a pipe nipple any Dia. you want and 2 caps for it. Either get end caps with holes to fit your airline fittings or drill and tap your own holes. Put a small screen in the pipe caps so the beads do not fall out through the air fittings. Screen could be window screen glued into the caps or even just a stainless pot scruber packed into the end of the nipple. As long as air flows free and screen blocks the beads from entering the airline is all you need.
Put one cap on end of nipple and fill with beads, put other cap on nipple with screen in place. Connect airlines, you now have a fast cheap easy dessicant dryer!
Build 2 or more, and change them anytime as needed or just daily as a habit.
With a quick couple on each end it would be easy to swap them anytime. Keep them capped if extras are packed and stored ready to use.
When you take a wet one off the line, open it and pour beads into a can or bowl and bake about 250-300F till they dry or if you have a large supply of beads just save them up till you have allot to bake all at once. They will turn colors when dry. I think what I bought has about 10% or more of the color change beads. If totally saturated I think it's about 1 hour to dry them.
I'll be making mine a bit fancier. Perhaps a 6" long nipple 4"dia. and caps with a T on each end with ball valves top and bottom, bring in the airlines from the side of the T. This way I can just disconnect the air, open bottom 3/4" valve and dump beads into a can, close bottom valve and open top valve and dump in fresh beads.
With a normal bulk line dryer at the compressor, the drain out bowl type, I should have little moisture getting to my disicant dryer so the beads should last fairly long between changes with a large nipple full. With 10lbs on hand I should not need to dry them very often, just whenever I get down to 2 pipe fulls left of dry ones then dry all the wet ones at one time.
When I was searching to buy my beads there were various types and ranges of beads. Search around for a good price, some places were far higher than others! Mine were in bulk bags, I think sold allot for flower drying but work as well for anything else like drying air or sucking water from 150proof alky feul
Mine I think are supposed to absorb 40% thier own weight in water, so my 10lbs of beads should handle 4lbs of water which is about 1/2 gallon USA.
My PC gun has the normal black plastic filter, I also have a filter with pressure adjustment on the coiled line to the PC gun. My Dissicant dryer will go between the compressors bowl type dryer and the T connections that feeds the PC gun, the blast cabinet, the blow gun, so everything will have dry air.