I'm trying my best to do this project cheap

I have a Dremel Pro, and a routing bit in the right size for the T-molding. I've been trying to find a Dremel attachment that would just make the line straight. It would seem that this is the first time I've ever needed to rout a groove in wood, and would feel silly paying $40-$200 for the ability to rout out these grooves.
I also considered going slowly by hand along a marked line. Sounds tedious, but if it saves me $50+ dollars, I'll ride it out. I work with tedious projects all the time (my business as a sculptor)