My inexpensive little Coleman two person dome tents served me well for hundreds of nights while riding thousands of dirt road miles on my motorcycle.
The riding buddies had fancier tents that leaked but mine never let a drop in.
The secret to my success was a double treatment of Kiwi Camp Dry.
After a very generous first coat that I would rub in with a sponge I allowed it to dry for a few hours.
Another coat was next including the sponging.
A day or two of airing out would render it waterproof and minimize the smell.
Whatever the tent, this product will improve it.
This link is for a box of ten cans.
You may have a little left over when used on a tent of the size you are seaking.
Kiwi Clear Camp Dry Fabric Protector 10.5 oz.
https://a.co/d/fX6ChNd