Bull Frog Snot's not the easiest stuff to use. (Sorry, couldn't resist).
My first application didn't go well, but the rest were better. The idea is to invert the locomotive and spin the drivers as low-medium speed while you lay a charged toothpick on the bearing surface of the tire. If you do it right, the resulting coating will be smooth. So, don't be dismayed if you try it and your early results are...well....awful. Use a paring knife or utility blade to pare it off and start over.
However, this product is best used on steamers with solid power pickup. If you have an older design with few pickup tires, the bull frog snot will only make things worse.
I model HO and Hon3. I'm not too happy with the performance of a few of my engines (mostly smaller steam). I am considering using a product called Bulfrog Snot. I'm told it works very well. Apparently, it was created by an N scaler...
Simon
A 4% grade is fairly steep, but I'm wondering if there's any room in your locomotive to add some weight, which might improve its pulling abilities.
I model in HO, which uses larger and heavier locomotives, but they also pull larger and heavier trains, too. There is usually room in those locos to add weight, which can make quite a difference to their pulling abilities.
Even a little space in your locomotive (perhaps between the top of the motor and the body shell), where you could add a suitably-sized piece of sheet lead, would improve the pulling power at a very reasonable cost.Sheet lead, in varying thicknesses, can be found at plumbing shops or roofing companies. If you want to give it a try, make sure that the lead does not contact any exposed electrical stuff inside the loco - Kapton tape is a good insulator, but even masking tape or electrician's tape would prevent a mishap.
Wayne
I am a newby to N-guage (had an 4' x 8' HO layout many years ago) and not an "N-gauge power user" like many responding here. Rather than focusing on being proto-typical, I just want a train that runs through some nice wine country scenery. My current layout has a 4% grade (1" per 25") which was not a problem until I bought two box cars and added them to my heretofore 3 railcar train. My only loco (an Atlas GP-30 diesel) started slipping about 3/4 of the way up. So not having anywhere near the budget to buy more locos at $100 each to add more power, I wiped the track down with alcohol which helped considerably to remove any accumulated oils, and then used some 400 grit sand paper on the offending section of track and that got the train over the incline, although there was still some slippage. I felt a slight hump near the top as the train enters a turnout, so fixing that will be my next sub-project. Good luck!.
- Mark