I use petrolum based products all the time to clean my rifles, without problems. The trick is to make sure you get the stuff out of the barrel before you load the first time. This is done with a simple patch dipped in Isopropyl (rubbing) alcohol that you buy at any Wal Mart. Swab the barrel with it, a couple dry patches and you're good to go.

As for the Hoppies.. go ahead and use it to clean your rifle. There are better cleaners out there IMO but it will work just fine. As for the Wonder lube, that is a whole different set of considerations. Personally I do not use Wonder Lube, Bore Butter T/C 1000 what ever you want to call it... other then to lube a conical now and then.

Another simple cleaner for your rifle is a 50/50 mix of Windshield Washer Fluid and isopropyl alcohol. You can swab the barrel with the stuff between shots, you can use it to remove fowling when you clean. And it will help dry the barrel between shots. Swab the barrel with short strokes between shots, then a couple dry patches and you can load again and get some great accuracy.

As for your friends rifle with the 1-66 twist, they are shooting roundball most likely. That is why they are using wonder lube. You with a 1-28 twist should concentrate using powerbelts, saber tooth conicals, maxi ball, and sabots of all different weights and shapes. A load you might want to try is 100 grains of Pyrodex RS and a 250 gr Shockwave. It should be a good load, but then all rifles are different so you never really are sure.