If you need extra support for your arm while painting, try a mahl stick. It's a simple tool artists you can either buy or make yourself.
The Mahl Stick - Sign Smith Sign Painting
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Guerrilla Painter Plein Air Telescoping Mahl Stick
Painting
The lightweight, varnished aluminum round stick does not easily bend after long use and the leather covered cork end is not slippery like rubber. Very
Artist Mahl Stick for Steadying Painter Hand 35 Inches in Length Aluminum Rod
Fine Arts & Crafts
EZ Rest Painting Handrest Mahl Stick
A wooden two-piece mahl stick for use as a rest or support, to steady the brush or hand while executing detailed or exacting work. The ball end of the
Handover : 2 Piece Wooden Mahl Stick : with Ball and Leather
Guerrilla Painter Telescoping Mahl Stick
How to hold a lettering brush and mahl stick : Robertsign
Gurney Journey: Mahl Stick
Technique Tusedays: The Mahl Stick - Principle Gallery
Fine Arts & Crafts
Artist Mahl Stick – Whiskey Painters