Cleaning them up can wait. Before one does anything at all, one should document their actual condition. A few photos can be a big help. In addition, one should at least measure the rim-depth (rim offset). Perhaps one could lay a straight yardstick across the diameter of the rim and measure the distance to the wheel-center.
After that, the dismantling and cleaning can begin. The spokes will probably be replaced anyhow, either by chrome-plated, powder coated steel or even stainless steel ones. You are well advised to pay attention to the quality, because your life may depend on the spokes doing their job properly. Certification that they've been tested by a technical testing institution is also not a bad idea.
The spokes on a wheel can vary greatly, e.g., two groups with different lengths. Determining this is very important, to prevent the threads from puncturing the new inner-tube. Of course, one must be sure of this before refitting the remaining rim parts. Any work, such as chrome-plating, must of course, be carried out before starting to do the lacing.
Before any subsequent, complicated work is done on the outer rim, the fitting holes should be examined. This of course, may also mean that the old outer rim is only still good for the scrap heap, unless, at least in the case of very expensive replacements, you are able to find an expert who can insert a bit of reinforcing.
When choosing the spokes and nipples, helpful information can sometimes be found, e.g., in the appropriate forums. Not only the material is important but also the take-up angle of the hub-side. The rolled-thread is added after the spokes have been cut to the correct size, the same as with screws.
Oddly enough, the biggest problems don't arise when lacing the rim, but afterwards, when centering it. One can of course, eliminate any twisting or off-center mounting and achieve the correct dish-depth of the rim by using the appropriate gauges, indeed, it is very doubtful that the job of tightening all the spokes to roughly the same torque can be carried out by the layman.
Even though one can do quite a lot of the work oneself, in the end, one will probably have to leave the balancing to an expert workshop. Bearing this in mind, it should be quite clear, that the renovation of spoked wheels is by no means a cheap undertaking. At least, by doing some of the preparation work oneself, one can cut back the expenses considerably. 12/13