Dinitrol

I have solved the problem. Simply... not enough sun/warmth. I took of the front end and let it stand in the full sun for whole of yesterday. By this morning 90% was what I expected - dry, "hard" (i.e I can indent it with my fingernail) and some parts still tacky but drying out. I think my mistake was doing it when it was too cold, followed by a cold week. So maybe this does work! But I wont do the underside until summer when it is warm again. I do minimal driving in winter anyway, and the underside is actually well protected. I spent my youth in Durban where I thought rust was bad, but gotta admit, the rust here with these salted roads is on another level.
 

First of all I disagree with what products you have used. The RC900 is produced to get at areas where you cannot get tool access. There is plenty access in these areas.

I would have rubbed down and used more normal rust convertor and left to dry, primed and left to dry then put on the Dinitrol 4941.

I did our 2016 Jimny by cleaning it down in summer 2017 and then applying Dinitrol 4941 and it dried within the day.

You don't want it to go hard because then it will just flake off and rust will form behind the coating. ln that case it's worse than having no coating at all.

The rubbing down I did 2 years ago when I did the first rust protection. Took 2 days on a ramp with needle gun, followed by electric drill with wire brush on day 3. Then rustoleum rust converter, followed by rustoleum epoxy. A month l later it received a further top coat of something my mechanic did but he went out of business so I did not get the product name. Whatever it was it dried "flexible hard".

I put the RC900 into the chassis box gerder and up inside the wheel arch, then the Dinitol vodeos suggested a light spray of DC900 and also a light spray of the cavity wax to act as a bonding agent. I opted for a single pass, light spray of DC900, not the cavity wax. I then sprayed the top coat of 4941. Maybe I should have sprayed on directly and not used the DC900 as a bonding agent?. Whatever, the result is a tacky, sticky covering. I expected something that was dry to the touch, would not leave a residue on the fingers, but if you pushed into it with your fingernail you would create an indent. Thats what I expected. It is certainly not what I got. Although I did just 2 passes, maybe this is too thick (I did not have a thickness gauge they refer to). Maybe too cold at the moment?

Today she sat with front to the sun, tomorrow again. Then I close her up. Hopefully over time this hardens. Luckily I did not do a big area and it is all hidden.

Thanks for the replies!