Building your own homebuilt aircraft means dedicating a huge amount of time, perseverance and resources into your personal project. Do not think that this can be done without too much trouble, it will not. It will take a lot of effort, time and dedication to finish.
By the time you are getting closer to finishing your project you must think about a paint job and even the registration it needs to have. And, more importantly: you made it, you can maintain your dream. Its just that simple and this will save a lot of money in maintenance cost department.
The registration you will find on an airplane is a combination of a country code and a country registration number (or letters). The country codes are assigned by the International Telecommunication Union (ITU), this is because they are also used as radio call signs and that part is governed by the ITU. The nationality marks are requested at the ITU from a list assigned to that state and then reported to ICAO, and we have a copy of the latest list here sorted in alphabetical and numerical order.
Having constructed your own airplane entitles you to do your own maintenance, obviously. Because you are the only person that has seen it from the inside and out and all the way back. Now it pays to have that knowledge and this saves a lot of money in maintenance department. But even in this situation specialized maintenance such as engine rebuilds or top-end overhauls and more must be done by specialized companies. These things are best done by professionals. Those of you with an aviation maintenance school background will benefit from that education.
Some people are concerned with the safety of homebuilt aircraft. Even the authorities made us install a placard in the cabin that it is NOT built to standards. Well, that is correct. Homebuilders usually have much higher standards and they build their project with love and dedication and not so much for a paying daytime job. Anyway, the safety records show that homebuilt are not unsafer than regular factory build airplanes.
Homebuilts are built from materials in these categories: rag and tube, metal, wood, or composite materials (fiberglass, carbon fiber, etc.). The first category is where the structure of the aircraft is built using steel (chrome-molybdenum 4130) or bolted aluminum tubes covered with Dacron fabric (some RANS Aircraft). This fabric can be painted to stiffen and protect it from UV light. The metal category is common for all aluminum built models like your everyday Cessna, Murphy or Zenair, although some parts will be made of composites (wheel pants, wingtips and fairings).
The most recent additions to the aviation fleet are made from composites, either glass or carbon fiber. This category is notable for its designs employing smooth and flowing body curvature and light weight which would not always be possible with the other materials. For example: the DynAero MCR-01 and MCR-04S are very nice looking and very fast flying carbon composite types.
And other manufacturers use a combination of the above materials. For example: the Falco from Sequoia Aircraft and it is mainly build from wood with composite layers on the wing.
Most of the tools used to construct an aircraft are quite common: electric and/or pneumatic drill plus drill bits of various sizes and lengths. Lots of cleco's (in 2/32", 1/8" and 3/16" inch) and a special plier to install/remove these cleco's. Drill stops are also very handy in preventing drilling too deep and keeping the drill from hitting the object in which the hole is drilled.
An expandable hole spacer can come in handy when a row of holes must be layed out at even distances, deburring tool (or drill bit), fluting pliers and safety wire pliers. In some cases you will need a metal shrinker/stretcher to create nice curves (as with building floats). A number of aircraft tool supply companies provide special tool kits, if you are a new builder these tools would be a good investment.
Your workspace must be well lighted, heated and ventilated. But this goes without saying. Most kit manufacturers recommend a certain size of workbench. Usually 4 to 5 meters long. Just follow those guidelines and you will do just fine.
Having layers of paint on your aircraft serves a couple of functions. The underlying surface is against corrosion protected and it really makes the airplane look great. The last statement is not completely true. There are some very beautifully build airplanes which are not painted and they look super flash when polished. A shiny aluminum look on a DC-2, DC-3 or Constellation is really perfect for those machines.
Preparing for a good paint job is best done when starting your project. You will need to make a decision on the type of primer/sealer that you are going to use and if it will be compatible with the topcoat you have in mind. The primer is usually used when building the aircraft from day one as it will be applied on the inside on some parts: think of aileron, flaps, wing etc etc. These parts will really need inside protection by a primer/sealer when its going to be parked anywhere near an ocean or sea. I have seen the effects of saltwater on aluminum and it wasn't pretty.