It will depend on the base fabric, but we did a refresh on our old Tepui RTT; I know it’s a different material but the steps are the same as far as I know.
We used Nikwax product, starting first with a wash with their “TekWash” product. TekWash seems pretty universal but I would confirm with the manufacturer what product is safest for your tent as they might have a specific recommendation. We washed our tent twice, just to be sure we got it all clean. To wash it, we just took it off the base of the RTT and put all the fabric into the bathtub with the cleaner product.
Nikwax Tech Wash Cleaner 300ml: Because it leaves no detergent residue, using Nikwax Tech Wash for all cleaning of your waterproof-breathable garments will help get the longest possible life from the factory applied DW
www.mec.ca
After that, we coated the tent in Nikwax Waterproofer:
Nikwax Tent and Gear Solar Proof Water Repellent 500ml | MEC
These two steps alone revitalized the tent, but we went the extra step and got a few seam sealer kits to re-seal the stitched seams:
Gear Aid Seam Grip+WP Waterproof Sealant and Adhesive 28g: Gear Aid’s seam sealer cures to a flexible urethane rubber, sticks well, and lasts a long time. It also works well as an adhesive to glue on repair fabrics. Moisture speeds curing.
www.mec.ca
Whatever products you use, I suggest the same steps: Wash, treat, seam seal.
Important Edit: I suggest these steps for a tent that has been used and whose factory waterproofing is perhaps wearing out. I wouldn’t see the need to do this with a new tent.
Hope that helps!