This paper introduces Painless Activation Steering (PAS), an automated activation steering (AS) method for post-training language models (LMs). Unlike existing AS techniques, PAS utilizes labeled datasets, making AS easy to use without manual prompt construction, feature labeling, or human intervention. Evaluations on the Llama3.1-8B-Instruct, DeepSeek-R1-Distill-8B, and Nous-Hermes-2 models and 18 tasks revealed that PAS improved performance on action-related tasks, with the iPAS variant demonstrating the strongest causal steering effect. Furthermore, PAS offers additional advantages over In-Context Learning (ICL) and Supervised Fine-Tuning (SFT).