Thank you for all those great and useful replies. I seem to remember reading on the West site (?) maximum of 6 pumps from each tin before mixing which meant about 150ml. I needed 4 of these mixes to fill the channel so I needed to mix then pour then mix then pour etc.
This means it all needs to be choreographed. If I could mix it all in one go and then stir with the drill and bent wire method that could have done advantages.
Shop vacuum and some vibration sounds interesting.

Maybe now I have a bit spare I can experiment with a method which combines all the good ideas above and still flows out before it starts to cure. Away from workshop until weekend do plenty of thinking time. Thanks again really appreciate it.

I'll try to capture whatever works in the next video to help the next guy out !