You are hereTube Method (Tomato, Video)
"Demonstration video of tomato grafting using tube grafting method
When you graft tomato plants, we recommend not saturating the substrate with water during the healing process to avoid excess turgidity of rootstock plants (due to the resulting root pressure) that could create a thin film of water at the grafted union, preventing the complete healing of the union. Relative humidity must be in the recommended range but wetting the substrate too much should be avoided.
In this video we demonstrated placing the rootstock roots in water during the healing process; however we do not recommend this technique for tomato. Too high root pressure of rootstock plants should be avoided as it sometimes reduces the success rate. Limiting irrigation for rootstock seedlings (not scion) before the grafting and during the healing is our current recommendation.