When you open the drains you are getting a blast of high pressure air with an oil water mist in it. Just putting the end of the hose in a bucket ends up spraying the water/oil condensate all over. You need something like the towel or the scrubby pads to diffuse the air blast, slow down the air velocity, allow the volume of air to exit the container fast enough, yet also allow the oily water to collect at the base without getting sprayed all over the next time you open the drains.
I drain into an equivilant of a square shaped plastic bleach container. fluid goes in and then when its air i can see the sides of the container swell. My drain lines are clear tygon tubing. you dont have to blow hard to do the drain.
in the pic you can see the clear hoses that go to the bottle, hope to have auto drains soon so that will require screwed on hoses on the auto valves.