Railworks America

You will more likely get a good answer here.

Just an idea...

Lay down something temporarily, like a road or track, along the length of where you'd like your slope.
Use the linage-tools thingy that allow you to grab the yellow anchor-point on it (for adjusting heights on roads, tracks, fences, etc..), then slightly/gradually raise the road/track on on end, approximating where you'd like the slope.

Use the paint-brush tools, enlarge the size of the paint-brush and another other options (such as falloff, etc..) with it accordingly, then use the terrain-snap-to option, and then run the paint-brush along the length of the road/track.
This should raise the terrain up-to the level of the road/track accordingly for that area.

When done, simply delete the road/track if you no longer want it there. Profit.

Well that's one way I might do it. Excuse if some of my terminology for the tools options I used in my explanation are a bit off, but I think you'll get the idea of what I mean.

Cool! You're welcome. Glad to be of help and that my idea worked for you.
That's how I sometimes "cheat" for making a slope or gradual incline for the terrain in some spots if I want it. Seems to work well enough. Then after I have the slope, I can adjust around the edges here-and-there with the paintbrush for raising, lowering or smoothing out some parts as I like. Cheers!