There are 2 ways to go sunward. You can shed speed to reduce orbital distance, but 30 km/s is a lot of velocity to change. Or you use another body (often antisunward) and a slingshot to put the craft in a highly eccentric orbit that, at times, is near the sun - so you have many proximal destinations you have to hit without error to meet your course. A mars transfer is easier but you want to hit certain proximity windows.
There are 2 ways to go sunward. You can shed speed to reduce orbital distance, but 30 km/s is a lot of velocity to change. Or you use another body (often antisunward) and a slingshot to put the craft in a highly eccentric orbit that, at times, is near the sun - so you have many proximal destinations you have to hit without error to meet your course. A mars transfer is easier but you want to hit certain proximity windows.