I think a big factor is the gear. This sounds like a plug, but it`s not. I use a lot of Geneza gear. It`s made from an MCT oil. There are other brands out there that use a similar carrier. MCT is super thin and disperses quickly. Some thicker oils tend to sit in the site for days. Even with little to no main, I can feel some oils for several days or longer. With some shots of Geneza Sust 270, which I`m using now, I hardly feel anything the next day and it`s long gone 48 hours later. Thats not every shot. Some shots are better than others, but this is common for me. 

Another factor, I use a lot of sites and I break my shots down to every day. For a "heavier" oil, like test 400 or one of the blends, such as Test e/EQ, I make sure those shots fall on days that I hit larger muscles like glutes or lats. On lighter days, I may use rear delts, delts, biceps, or triceps. Quads are kind of an in between muscle for me. The fibers aren`t as flexable as glutes, so I don`t fill them with quite as much oil. 

I try to give each site 6 days off. More if possible and more if needed. 

For gear that doesn`t cause much irritation, you may want to consider doing a small amount sub-q. Start out with 1/4cc and see how you respond. Sub-q is an easy way to add more MG`s per wk

Exercise helps too. Working a muscle that has gear in it, helps to carry fresh blood in and break the oil down. Plus, as you are already doing, massage work. Add to that, the foam roller. They are a great tool to use daily