I've been looking into Krita recently, and been very impressed with many of its tools, like multibrush and 'digital colors mixer'. I'm considering moving from MyPaint to Krita for doing the bulk of my artwork, but there's one stumbling block: There isn't a way to change color or brushsize while the pen is down, which I find very useful in quickly sketching out the basic values in landscapes and plants.

By comparison, in MyPaint you can hit one of the 'color change' or 'brush size change' shortcuts and it takes effect immediately. In Krita it seems I have to deliberately stop drawing in order to change color or brush size.

I hope I am mistaken about this -- Can you help me to get this working?

No, not while the pen is down. Nobody has ever asked for that before, so it is not strange it's not available. Until now, everyone was plenty happy with the set of options Krita has: size by pressure (of course, that is when the pen is down), shortcuts to change brush size (, and .), shift-drag, top-toolbar slider. Frankly, I have never even tried to resize the brush with a shortcut while drawing a stroke, not in Krita, not in MyPaint.

I appreciate 'size by pressure', 'opacity by pressure', and 'luminosity by pressure', but they give a quite different effect to actually changing the base size or brightness (or in MyPaint, moving through a sequence of colors in the palette) -- in particular the 'pressure' effect is difficult to control, while keyboard adjustment produces discrete steps in size or brightness. The result is that while I can obtain similar results, the workflow contains much more 'click/pen-up' events and the visual flow of the drawing is more fragmented..

@finticemo
I was having the same issue at first, resizing using shift drag is laggy and not very precise (at least for me). What I end up doing was changing the shortcuts of "Decrease Brush size" and "Increase Brush size" to "S" and "D" respectively. While painting I just press the shortcuts the number of times needed to change the size as I want. The increase and decrease curve is well thought and it mostly resizes as you expect it to do. (Gimp changing curve is one of the two, very little, or extremely wide stepped).

While you can press the shortcuts while you paint and the brush outline will update, the size won't update until you release the click event and click again.

Changing the shortcuts In this way you don't have to mix one movement to do 2 different actions. (drag is very similar to draw ).

@boudewijn
I just wish I could change <shift> to pick colors and CRTL + ALT + drag to change brush size. (I think open canvas worked like that, but im not sure, it's been a while since I used it). CTRL is a "pinky" finger bit too far from the resting position of the left hand to be usable. (on my way of working, "ala blender" one hand in the keyboard the other in the stylus)