Originally, I started off using the diluted paint method posted awhile back. Basically, you take Tamiya clear and mix in a little bit of regular Tamiya purple to make purple water (very heavily diluted purple). Then dip the canopy in and use a paper towel to soak up the excess.
It does give a good result, but being as clumsy as I am, I was kinda slow at soaking up all the excess to ensure an even finish. The mix starts drying and quickly starts becoming sticky, making it hard to soak up any more.
So I made another mixture but this time I used Future instead of Tamiya clear. I'm well aware (obviously) that Tamiya acrylic has a tendency to clump up when mixed with Future. Well, I pressed on anyway and spent a few minutes stirring until it was as dissolved as possible. I just let it sit for a minute and any remaining clumps settled to the bottom. Then I dipped the canopy in (taking care not to scrape the bottom), soaked up the excess, and voila! Purple tinted canopy.
The watery nature of Future made it easy to soak up the excess and get the even finish I wanted. It took me a few attempts to get the right amount of purple, but luckily Future can be washed off easily with water before it dries. Also had the added benefit of simultaneously sealing in the purple tint.
I recommend the first method for a decently skilled modeler, and the second for clumsy fools like me.