,
Mix  Shellsol with linseed or walnut oil to create a generous flow medium  - 
depending upon how 'washy' you want the medium -  you will need to experiment with the quantities before embarking on painting. I would also check for drying times, and if too wet - experiment with adding some liquin to the mix.

This preparation is one that I have used for many years with great results - easy to make and the paint not only moves easily across a variety of surfaces but adds to the lush characteristics of the oil paint.
[I have also used this preparation to make putty medium].

1v of Liquin Original [Winsor & Newton]
1/2v Linseed Oil
1/2v Stand Oil
Blend well - make sure to mark your container/jar with the recipe and note as flow medium.

​Putty Medium

Using a clean large board [white tile or formica shelving is good] or large plastic plate
Add a cup of calcite to one side 
In the centre add your flow medium - a quarter of a cup
[I also make the putty using Stand Oil or When I have cleaned my own oil - refer to the calcite sun oil website - I use that]
Slowly with a palette knife bring small amounts of the calcite over into the oil and work well until absorbed into the oil - continue until the oil looks like putty - it should reach the consistency of chewing gum.
Put the putty into a glass jar and seal with a tight lid. 

I use the putty medium in equal amounts- 1v of putt to 1v of paint - it will extend the amount of paint you use and at the same time provide the paint with extra body - if you use the recipe with the liquin as mentioned above you will have the added benefit of the paint drying faster.

http://www.tadspurgeon.com/
http://calcitesunoil.com/

Check out both these sites they have some information that the professional painter and visual researcher who is interested in materiality will find valuable.

Rabbit Skin Glue as a Size

• 1 v of glue to 10 v of cold water
• [if adding alum, which will make the size waterproof, use 1 v of glue to 8 v of cold water
• [approx 5grms of alum to 2 v's of water]  the extra 2 v's of water can be added to the alum, which can be added to the glue after it has set and is in the process of being heated. 
• Dissolve the glue with the cold water - gently disperse with you hands [wear plastic gloves]
• Set over night -[ it should look like apple crumble when set]
• I use a rice cooker to cook my glue - put on to heat - do not let the glue boil - it should be heated to around 60 degrees [ you should still be able to put your finger in]
• The glue should last around a week if refrigerated

Rabbit Skin Glue Gesso -courtesy of Pablo Tapia

Using Rabbit Skin Glue Size as a base - heat till warm:
1 volume = 250ml
 
1 volume of glue to 1 volume of calcite [* you can add 1/3 v of Titanium White to the calcite: 2/3 calcite – 1/3 TW]
 Add the dry materials to the warm glue and mix well until blended
Once the gesso has reached a creamy solution add approximately one teaspoon of glycerine to the gesso – this well reduce the porosity of the gesso, as it is very absorbent.
 
*When applying the gesso ensure to apply a coat to the back of your board to avoid warping – apply between 4 and 12 coats of Gesso – smooth the surface with a pad of muslin that is damp  – apply using a circular motion.

*To seal the gesso ground you can do one of three things:
 

• Apply to coats of skim milk sequentially [a third coat with pigment added would act as an imprimatura]
• Apply one coat of Rabbit Skin Glue Size in the volume of 1-30 [weak]
• Apply Linseed oil repeatedly until the surface cannot absorb any more oil.

 

Before I go into any great detail with recipes and any other materially relevant information, I thought I might position my relationship with materials, mediums and other substances, sometimes used in the practice of and observation of painting........as a fusion of old meets new - voila - and there you have it - a personal material methodology honed out studio based practice.

Painting will kill you - yes that's correct, if you do not practice safe painting that is exactly what will happen - lung disease - your hair will fall out [ my bald friend PT told me that] but seriously, young students in particular - right from the word go -PRACTICE SAFE PAINTING.

I am a devotee of a non toxic studio environment - if you follow safe painting practices you will find yourself catapulted back in time to a place where the Old Master Painters used, not always, but current research illustrates that they used fast drying - natural and non toxic materials and mediums in the construction and conditioning of paint - lets not forget lead paint you say - and of course I acknowledge that. However, if we 'research' the material methodologies of our fore fathers you will find not only supporting documentation that will assist in your studio based material research but you will expand your material knowledge base,  AND through a process of discovery - you will begin to develop your own personal painting METHODOLOGIES.