The paint looks good Pascal.
Bob, in order to get a shiny finish you need to add a reflective material in Max and give it about 20% reflection. Any paint used in that composite material will be shiny. Shiny is not the norm, so it has to be a special Max version of the aircraft, it cannot be just reskinned if you want a flat finish later. The material combination (diffuse plus reflective) is exported with the model file and can only be changed in MAx.
Urraco, I have found in the past that trying to use meshes made by others for aircraft is not really an option. Apart from copyright issues, free 3dsmax meshes have far too many polygons. The only way to reduce polygons is to weld the extra verticees together to simplify the mesh. Because of the number of polys and therefore lines in the mesh it is impossible to see what you are doing. I make all my own meshes it is usually faster than trying to fix another mesh.
If the model is from Sketchup, it probably has 30,000 plus polys, and while it can be brought into Trainz, it is not legally possibly to get it into Max to work on. Again, the shear size of the correction task is not worth it, sorry.
Of course a from scratch Embraer 145 might look like this in Max

:
There are some new aircraft available, I have been spending some time on air refuelling tankers with Rob. He has done some texture work for this one, the KC10A Extender:
The aircraft is set up only to connect to the larger freight carriers such as the C-130 and C5A Galaxy. Using the keys, the tanker will rise above the track and extend the probe for coupling (on straight track of course!). The picture was taken while testing the tanker, and you are in and out of Driver all the time - I did not bother to start up the Galaxy (you might notice the crew have the door open with the steps down) .
The next one now available is the Airbus A330 MRRT tanker aircraft, this is used by the RAAF. It is a little more complicated. It will refuel aircraft from either the center fuel probe or the wing fuel probe on the right of the aircraft. Using the V key lifts the tanker and extends the center probe for coupling with the fighters, FA18, Sukhoi35 or Tomcat:
Then using the H key the tanker moves sideways and extends the wing probes to couple with the fighter:
The models are startup versions of course. I will upload the Vickers VC10 K3 Tanker tomorrow, it is similar to the above but only uses the wing refuelling probes.
You can see all the details and trigger settings on my webpages. Look under the Military Aircraft, Jet Engined for these three aircraft:
http://ianztrainz.com/aircraft-standards/
Ian