15 minutes is a safe max time to run the puffer smoke on my Railking steamers.
As far as spitting fluid out of the stack , I now have no problem since I use the tiny funnel that I found in the packaging for my Railking ps2 Triplex. It seems to go way down iinto the recesses of the smoke fluid reservoir.
I have tried the plastic droppers and even the droppers in the fluid bottles but I guess I just like to count the " drops " as I fill the reservoir.