Just use a long ass needle, find the head of the muscle, inject and massage. I have a friend who used a very tiny amount to get some "pop" to his muscles. Very, very minuscule amount. And he looks fantastic!!
If you use a very tiny amount just to keep the muscle constantly pumped, I think you can get away with synthol usage. My triceps are really lagging and I've always considered it. But I'm still going to plug away in hopes I can find a way to grow them. Don't want to fuck myself up permanently for a little mass.