Agree with Splendid cruiser, 100%. I have to say RANT was the way for me. I thought, (just MY opinion) Vortex was pathetic. RANT allows you to not worry about flying the aircraft. Rather just interpreting the needles. Honestly, it was priceless for me, and I would say go back to it. NDBs holds become a non-event...
Flight Sim doesn't have ADF dip, and some of the coordinates are a little confused, meaning some approaches simply aren't accurate at all. (The Exeter NDB approach. DME is wrong when overhead the Beacon. Bournemouth departure to Thred. Fly it perfectly, and in FSX, you'll miss the intersection by miles.)
Instrument Flying Background To IR And IMC
This book was recommended to me years ago, pre-IR, and while some of it is odd, it makes clear a lot of things. (As great as Rant is physically, I didn't find it's written explanations straightforwrad at all. Rather, gibberish, so I do sympathize.)
GOOD LUCK