Getting “rusty” is a common problem even for old dogs like me. There is an easy solution and I have adopted a motto I found on an application I use often and that is “Do something everyday even if it sucks”. You don’t have to save it, but hold on to it long enough to determine what the biggest problem is that you are facing. This is why I taught my students to keep a sketchbook with them at all times so every spare moment became a chance to build skills, experiment with a new object, practice values modulation, etc. The sketchbooks come in all sizes and I use pocket sized, backpack sized, and studio sized, old and new, falling apart and brand new never touched waiting for when I use the last page of the one I’m using now. You can find them at WalMart and art supply stores. I usually buy mine at Michael’s when they are on sale. Never leave home without one along with one of those handy pencil bags that WalMart sells in the Fall filled with at least a pocket pencil sharpener, a couple #2 pencils, a pink eraser and a white vinyl eraser, a cheap grade school compass, a 6" plastic rule (straight edge) and/or anything else you enjoy working with. Make it easy for yourself to constantly build skills and avoid the rust.
Coolidge Agate, Acrylic on panel, 96"x 48", c1992