I cannot say enough good things about the VEVOR fr900k continuous sealing machine. It works so well that I look for things to seal with it!
There is not really any instructions, but you can find a video on YT.
This unit heats quickly, can be tailored to your bag via heat setting, belt speed and belt height. Seals quickly and effectively. I use mine for everything from 3mil clear poly bags to 7 mil mylar bags with just a small temperature adjustment.
If you are even considering this machine, buy it. You will save so much time and energy using this over a manual sealer