Those suction type setups are shite IMO and I'm not a fan of Eastwood stuff in general. The yanks love Eastwood but a lot of their products are aimed at inexperienced folk who hear that Eastwood are good.
Anyhow, blasting firstly depends on the size of your compressor cos a bot blaster such as this Pressurised sand blaster
will work far better than syphon or gravity feed guns such as this
Gravity type gun
If just doing small areas buy one of these guns and some iron oxide or red garnet from a blasting supplier. Will be much cheaper than what tool shops sell the shit for.
At 90psi the hopper of the gun will blast 25-40cm2 before refilling depending on how rusty the area is. It will struggle on deep rust though.
I've used both gravity gun and pot blaster and the pot blaster is far superior but then I have a 17CFM (460LPM) compressor to be able to run a pot blaster. The 120/150LPM DIY compressors will not run a pot blaster properly and will still be constantly running to keep up with the gravity gun.