No, nothing to paint onto it, and yes, you can cut it down. One here was reduced from 25 feet down to a stump about 2 feet high with everything removed and it recovered - but hasn't flowered, and that's the risk, you might not get any flowers for some time. This work was also done in autumn, when there is less chance of excessive bleeding, which might happen if you do yours now - would have been best to do it mid winter, when the sap was down. Angle the cut you make to allow rain to run off.

It's a pity you missed the boat for pruning this, last Dec/Jan. But as your Wisteria is getting into the eaves you have no choice but to cut it back or risk damaging your roof which will be costly.

I'd begin by getting rid of that thick branch that extends downwards to the right. In fact get rid of all branches growing near or into the eaves. Then cut all the old branches back, say down to the half way level of the middle window. That will retain sufficient branches and stems and foliage (to come). The Wisteria will react by throwing out large numbers of long stems from the remaining branches. Let them grow until August then shorten the ones you don't want to develop into new branches back to 4- 5 buds. The remaining few stems you might want to retain as new branches around the right corner below the window. The next real big pruning to shape the whole thing will be next winter.