I too build mostly 1/48 aircraft. I approach each build with consideration on how best to hold and/or set on stand for painting. Many builds require several techniques. There are some more common methods and these can be modified for each new build.
For single prop aircraft I attempt to secure a rod or clamp into or onto where the prop will eventually be installed.
For many single engine jet aircraft a pencil, rods of different diameters or coat hanger wire can be inserted into the rear exhaust or front intake.
For dual engine jets, I have used coat hanger wire bent into a loop so I can insert into both front and rear of the jet and bend the wire to make a stand of sorts. I will wrap the wire in foam where it enters the model so it will not damage the finish.
Sometimes I take the box lid the kit came in and cut notches on two sides to create a cradle.
I have used larger c clamps and clamped the aircraft nose to tail or wing tip to wing tip.
A cheap lazy Susan will be invaluable when your aircraft is on a stand and you need to rotate your work.
Once I had a larger aircraft and decided to hang it using cloths line and clamps so I could paint it standing up in the garage.
Dense foam and toothpicks or bamboo skewers allow you to make all sorts of odd shaped stands. You can cut the foam to shape and assemble the foam parts using the toothpicks and skewers.
Get creative and you will find many household items that can be used.