Not sure if there's a good way of doing it, but it is possible..Would say it depends on fast fingers and luck.
Prepare your 2 attacks, 1 in each tab, just like you would do on a normal computer.
Hope that when you press send on the first one, that your connection 'lag/become unstable' and you can switch tab and send while your connection is unstable...and they should be in order once they finally load.
if there's fast and more reliable way of doing it? Probably, but the one mentioned above is what I use.
I have tested my method and once you get the hang of it, it's possible to do it most of the time, but still not 100% reliable.