For EQ I always look at the 200-500hz range since it can get really muddy if there is too much in there. However, if you want to soften/darken the piano I would try a high shelf, or if you want to keep some of the higher end and want to remove some of the high mids then use a wide Q bell shape.
Compressors are really tricky to recommend settings but you would want to play with attack, release, threshold, ratio. I'd probably start by bringing the threshold down more than you would want so you can hear it working, raise the ratio fairly high (like 4:1 maybe), then play with the attack and release, maybe 20-30ms attack and a longer release, maybe 100-150ms. Once it is behaving how you want, raise the threshold until it is only affecting what it needs to, and then decrease the ratio so it's not so aggressive. Really depends what you want to get out of it though and many other factors. There are many approaches too, you could go for high ratio and high threshold (often useful for dealing with peaks) or low ratio and low threshold (useful for levelling). You can also do parallel compression so you mix a fully wet and usually heavily compressed signal in with the original dry signal, this will raise the quiet parts but keep the dynamics of the overall sound. You could also look at different types of compression, RMS might be useful for you.
Whatever you do with the compressor, set the makeup gain so that when you disable the compressor the level is the same as it was before, this way you are not tricking your ear by mere volume and can accurately judge whether the effect is doing what you want it to by bypassing it and enabling it again. I like to close my eyes when doing this and hit bypass a bunch of times so I don't know when it is enabled, and then choose which sounds better, if it's not the enabled version then you need to change things (or not use it at all).