Force a draw - outside of the ::draw() method?

I have a function in my ofApp which loads some stuff from disk, and performs some initializations. In doing so, it completely hogs the default draw() method for about 5-10 second, which I've confirmed with:

void ofApp::draw() {
    ofLogNotice() << "   draw! ";
    ...
}

Basically, no message is output during while initialization function does its stuff and hogs the rest.

I am aware that this should probably be solved somehow using threads, but for now, I'd just like to draw a line on screen, to indicate something is happening. Initially I would have added an ofDrawLine in the draw() method, but since it doesn't run while hogging, it doesn't help me with much. So, I thought of inserting ofDrawLine directly in my function that inits (and hogs):

void ofApp::LoadAndInit() {
    ofSetColor(ofColor::green);
    ofSetLineWidth(3);
    ofDrawLine(50, 50, -50, -50); // start indication
    // do hog stuff part 1
    ofDrawLine(60, 60, -60, -60);
    // do hog stuff part 2
    ....
}

I would have expected the lines to overlap with the last rendered image (as the full draw() is not called, and the rendering process would not clear the window) - however, I am not having anything shown at all.

Is there anything I could do (maybe call some function), so that the ofDrawLine is forced to draw from this function - regardless if it is not called from the actual draw()? I tried using events().notifyDraw(); after the ofDrawLine, but unfortunately I still cannot see any of these lines drawn...