I write on guitar. Any advice on how to write songs on piano? I can play piano okay. Easy songwriter songs or progressions to learn on piano? Easy artists or albums?
I dunno. You might start by trying to translate some songs you've written on guitar for piano. The few times I've written on the piano it's usually because I want easy access to melody and chords together. I don't learn any special chords on the piano, but maybe learning how to build the different chords... like how to build a major or minor chord starting on whatever pitch you want. Piano is really a great instrument to learn theory on.
Come up with cool rhythms. Either in chords or in the melody. Piano is cool for that.
Actually, just using a different instrument, even if you stick to your normal patterns, can be refreshing.