I was excited to see your question, my wife has had the same issue and can't seem to get the whole squirt thing dialed in. I think you are on the right track, I have always heard it is a product of masterbation not oral or actual sex. I am looking forward to seeing th answers on here
My suggestion is not to try to squirt, you need to try to keep masturbating and don't stop. In the process change things up. Work on your clit, then go to working on your G-spot. I think the whole key is to just plan on spending the entire night playing with yourself. Think of it as you love everything you do and got to keep going. What is the most time you have spent masturbating? Keep us posted on how things go for you.