Touching up a testor's red enamel spray over darker acrylics

[Zeller]

I've been using testor's guards red on my blood angels for years now but I still don't have a viable way to either touch it up or remove accidents. For example, I am painting a piece that is brown or boltgun and I get some on the arm. The red won't cover it up no matter how many coats I use. I've got a bottle for minor fixes but the pigmentation is insufficient and leaves panels looking semi-transparent or splotchy. 

 

What can I do to fix the red without having to strip the model and start fresh? Basing the army is also a huge issue since the base colors get on the feet and lower legs. GW paints would have been smarter and easier to fix. On legs in particular, would it be practical to cover up the mistakes with weathering powders? I haven't used any on the army yet.