I also use the DeKup system on my Devilbus Finishline 4 plus both my Sprayit guns. While the liners are disposable the real advantage to me is I keep several full of the finishes that I use the most - Mohawk Buffcoat and Target 8000
Plus I keep one full of water and another full of lacquer solvent to flush the guns.
Between coats, even if that is going to be overnight, I leave the finish in the gun and if I remember I spin off the air cap and place that in a small dish of solvent or water - this is to keep the air passages clean
When the job is complete I removed the finish cup and store it - if it is below half full I normally fill it up and store it full. To clean the gun for waterborne products I install the cup of water and spray it thru. For solvent products I install the cup for of solvent, disconnect the air and let the solvent flow through the gun. And is a great tip that Willemjm showed me - the solvent goes directly back into a gallon of solvent that is marked for cleaning only. There is no wasted solvent and no need to blow a cup full into the air.
Try it - you will find this process to less than two minutes