This question comes up quite often. Try the search function on the forum and you'll find some great info
You can just enclose the tank and stand with plastic sheeting. Make sure it's 100% air tight and then some. Don't run the skimmer during or for a day or two afterwards and run carbon during and afterwards too.
If you think it's sealed up tightly enough, seal it up again [emoji28]
Ask the fumigators in advance too as they should have some ideas we reefers won't have. I bet they get asked that more often than the forums do!