Some tips and tricks I've come across which some may find useful...

Oil painting...
 
Oil painting offers me the most possiblities but for years the turps and white spirit fumes gave me headaches!  I discovered Orange Oil based thinners which do a better job and smell great!

Available from:  Atlantis Art materials - Click to visit site

The oil paints that I use are made by Michael Harding and are the purest and brightest I can find.

Available from:  Atlantis Art materials - Click to visit site

 

Lino etching with Caustic Soda...  
Working with Lino etching over the years, I've discovered that mixing a liquid solution of caustic soda and (for example) powder poster paint facilitates more control over the bitten area of the lino. Successive applications create deeper bites and increases the possible range of tonality.