Current DSL environments lack smart editing facilities intended to enhance modeler productivity and cannot keep pace of current developments of integrated development environments based on AI. In this paper, we propose an approach to address this shortcoming through a recommender system specifically tailored for textual DSLs based on the fine-tuning of pre-trained language models. We identify three main tasks: identifier suggestion, line completion, and block completion, which we implement over the same fine-tuned model and we propose a workflow to apply these tasks to any textual DSL. We have evaluated our approach with different pre-trained models for three DSLs: Emfatic, Xtext and a DSL to specify domain entities, showing that the system performs well and provides accurate suggestions. We compare it against existing approaches in the feature name recommendation task showing that our system outperforms the alternatives. Moreover, we evaluate the inference time of our approach obtaining low latencies, which makes the system adequate for live assistance. Finally, we contribute a concrete recommender, named ModelMate, which implements the training, evaluation and inference steps of the workflow as well as providing integration into Eclipse-based textual editors.