With the runway and taxiways painted the obvious next step is to mark them up with the correct linework. I have found that paint pens are absolutely marvelous for this. You can use a ruler with them, they produce lovely thin lines, are quick drying and there's no clean up. Of course if you're doing linework it helps do to some homework too and there are several resources available online to help you get the right look and feel.
There are various documents available online to help design your taxiway, runway and gate markings with an air of reality about them. I have two myself - one from the USAF Headquarters Civil Engineering Support Agency and one from the US FAA (Federal Aviation Administration). For my limited space without either end of the runway the markings are actually surprisingly simple. As you can see below item B gives the length for the centreline markings which are white and in real life measure 30.5 metres:
In terms of taxiway centrelines and edging the colour is yellow with the check bars only at curved portions of the taxiway edge (they appear to go all the way in the diagram below but checking lots of airport photos shows that's not the case):
Intermediate hold points on the taxiways are simple dashed lines typically at junctions to illustrate when an aircraft ought to stop. Below you can see an example behind the Shenzhen 73H's tail and beyond the left wing. Road markings are as you'd expect in white:
Lastly runway hold positions are more complicaed with two yellow lines and two dashed lines close together:
The last part of detailing that is still missing from the diorama are the taxiway and runway designator markings telling pilots which taxiway/runway they are turning onto. I may even get some of the taxiway signs that have been available at http://www.maqualas.cl . Once that is done this part of the diorama is completed and it'll be time to move onto phase 3 of Xin long - a new terminal complex! You can catch a sneak peek of planning for the new terminal in the background of the photo below:
This blog illustrates my tinkerings with my various model airport dioramas and discussion of the model manufacturers output