I have used Sig dope and Randolph dope, including the Sig and Randolph branded thinners and retarders
The dope was applied per the directions and it looks real nice.
However all is not perfect, the dope is not fuel proof to raw fuel.
I have not had any issues from exhaust residue but if raw fuel or raw alcohol gets on the finish it will melt it.
I am heavily invested in the Rabdolph products right now so economically I will need to use it before moving on to something else.
That something else is going to be the Stits Poly-Coat products.
Here is a link to the website http://www.stits.com/store/index.html#36
I may be the only one here that has had this issue with the dope, but it has been with two different brands. If I had found the Stits products before i spent so much money on the dope that is what I would be stocked up on right now.