Looking through my “The complete reloading manual for the 30-30" it has these loads listed for Varget powder.
Sierra has a load listed with Varget for their 150 grain bullet as “28.8" for a starting load to “34" grains as a Max load. Rifle used for the testing was a Marlin 336 with a “20" inch Barrel, using Remington cases and Remington 9 ˝ large rifle primers. Trim to length is 2.029
The Hodgdon powder company lists this load.
150 grain Sierra bullet starting load is “31" grains to a Max load of “34.5" grains. Rifle used is not listed. It has a 24 inch barrel. Primer used for testing is a Winchester Large Rifle. No case used was listed.
Always use starting loads, then work up carefully.
As to your question about if Varget is a good powder I couldn’t tell you as I have never used it for the 30-30. The powders that have worked for me in my 30-30's are Winchester 748, H335, IMR 3031 and IMR 4064. These are used between two 30-30 rifles. A Marlin 336 and a Winchester 94. I use different bullet weights and different powders for each combination between the two. If I were to just use one powder for both my rifles with the 150 grain bullet it would be Winchester 748, which is what Winchester uses for their factory loads. You might mention to your friend that he should get a loading manual.
Happy Shooting
Little Joe