Machine cooling /lubrication.

The main purpose of "suds" is to cool the tool.
As such, it should be applied as a generous and continuous flow so that it conducts heat away from the
cutting tip as speedily as possible..
A fine mist does little to cool the tip, and a "drip" feed can cause heat-fractures, especially on tipped tools.
The simplest feed mechanism is gravity, from a tank which should be as high as possible.
If the suds from the drip-tray flows into a second tank, the tanks can be swapped when necessary.

Traditional "suds" is very effective but can cause corrosion if left on the bed, slideways etc.
The corrosion is caused by a bacteria which feeds on the oil, so strengthening the mixture does not help. The only solution is to thoroughly clean the machine, including felts, etc, if it is not going to be used for a while.

There are other oils which do not cause this problem, and although they are slightly more expensive, the quantities used by the amateur would still mean that the cost is minimal.

In an emergency, soapy water, or even beer can be used as a substitute for suds, (although I cannot conceive of any emergency that would warrant such waste).
Milk can also be used, and some people reckon that it is a good lubricant for bronze and aluminium.

RUST REMOVAL.

Most methods of removing rust are abrasive, and consequently also remove sound metal.
This can leave a smooth surface, but  often this isn't important, and retention of the original metal is preferable.

A simple method of removing rust, is the electrolytic method.
It is ideal for heavily rusted items that are to be painted afterwards.
It turns the rust back to steel, rust scale is loosened and will fall off or can be easily removed.
Metal which is not rusted is not affected in any way.

(NOTE: In most cases, it will also remove any paint that is on the item.)

EQUIPMENT.
Water
Washing Soda
Battery charger
Stainless steel plate / bar
Plastic container large enough to enable the rusty item to be completely covered in the solution.

Add washing soda to the water at a rate of approximately 1 tablespoon per gallon of water.

Clean off an area of metal on the rusty item to enable a good electrical connection to be made.
Attach the NEGATIVE wire of the battery charger to the rusty item.
Attach the POSITIVE wire to the stainless steel plate or rod

Immerse both the rusty item and the stainless steel in the solution, and connect the battery charger.
If the charger has a meter, a small current will be seen to flow.
Small bubbles will rise from the  rusty item, and within a few minutes the surface of the water will be covered with "froth".
The rust will be removed quickest on the surface facing the stainless steel, although all the rust will eventually be removed. However, it may be quicker to turn the item round so that both / all surfaces are facing the stainless steel.

The time required to de-rust an item will depend upon its size, the amount of rust, etc, and may range from a few hours to a day or so. If the rusty item is left in the solution longer than is required, it will not come to any harm, so the timing isn't critical.
In fact, neither the strength of the solution nor the current are critical, so it is a simple and "foolproof" method of de-rusting.

After the item has been in the solution for the requisite time, wash thoroughly in clean water and brush off any residual rust, paint, etc, that is still attached..

As the item will now be clean, and wet, it should be dried and painted as soon as possible, before it rusts again.