Hey, I'm trying to create a grayscale filter on top of everything, so that I could flip it on and off to check my values. Any help would be appreciated!

I'd suggest Adjust -> Desaturate. It has a variety of desaturation method options.

Yes, that filter used as a filter layer should do exactly what you want. See https://docs.krita.org/en/reference_man ... ayers.html

"For example, if you add a Filter Layer, and choose the Blur filter, you will see every layer under your filter layer blurred."

This is the part I'm struggling with since I'm working on multiple layers. I'm trying to figure out how to add the filter effect to every layer. I tried to create a new layer and add filter-> desaturation in hopes that it would affect all the layers below it but it seemed that wasen't the case.

Filter Layer is what you want in this case, not Filter Mask, those are two different things.
A Filter Mask applies only to the layer you added it to, not the whole layer stack below it.

Lynx3d wrote:Filter Layer is what you want in this case, not Filter Mask, those are two different things.
A Filter Mask applies only to the layer you added it to, not the whole layer stack below it.

So, suppose my initial question boils down to: how do I go about creating a filter layer to quick check my values?

Select the layer at the top of the Layers docker and then go the bottom of the layers docker to click the small down-arrow next to the '+' icon.
Choose 'Filter Layer'. This will add a filter layer to the top of the layer stack and open a window that lets you choose which filter to have in the filter layer.
Expand the Adjust group and choose Desaturate. That will give tyou a choice of a variety of desaturation methods. Someone else may knwow they best one for this purpose but you can try to see which one seems good.
Later, you can select that filter layer and press F3 to open its Properties window and change the desaturation method if you want to.

Alright, problem solved! Thank you everyone for pitching in!!! This would have taken me aeons to figure out by myself.

Cheers. Jakke