The eastwood stuff comes with a extension tube to apply the product in tight area plus it will ooze down in seems before it starts to solidify into a waxy consistency hours later definitely a consideration for long term protection.
I was thinking of this product too for various areas. Areas I cannot get with this other method below:
The other method an old-timer Body man showed me and I have used it on an old Regal door that basically needed replaced. His method was to remove all the rust possible by whatever means required. My 85 Regal door skin lower edge was basically rusted off so I cut open what was there by rolling back the edges of the door skin. Removed all the rust by chipping, grinding, sandblasting and then I sectioned in a lower door skin edge. Just before rolling down the door skin, I brushed FIBERGLASS RESIN in the overlap and rolled/tamped it down while it was curing (you have to work fast) Then I mixed more resin up and poured down into the bottom channel and tipped the door back/forth to spread it around, thow-away paint brush helps in spreading it too. GRAVITY is your friend, rolling the door around, the resin flows like water, deep into the crevices. (obviously, the door is off the car) Cleaned what comes out the door drain holes with lacquer thinner & let it cure. Mix more resin and did the front edge of the door, let cure, mixed more and did the back edge of the door. Normal, thin bead of body sealer at the edge of the door skin when resin was all cured. Sand, Prime & Paint
That was in 2005 and 10 years later, the "Daily Driver", not driven in winter car, that door is just as solid as day 1.
Richard