Personally my stomach never could handle cough syrup, much less downing a whole bottle at once. The best way to do it is to get coricidin cold & cold pills (cvs has a generic variety). Take 6-8 (tolerance goes up too fast. you'll do 20 soon) of those and you'll be messed up. Smoke some herb first to calm your stomach if you're sort of sensitive to this sort of stuff. If you have an iron gut, then disregard.
Don't go buying/stealing just any cold pill and thinking 10 or 20 will mess you up in a good way. You can seriously damage your organs, or have a heart attack. This is one reason why coricidin brand has been used; its for people with high blood pressure, so you can take 12 and not die. If you have high blood pressure don't do this stuff.
I never had any crazy visuals unless I was mixing a variety of drugs. Straight Triple C's (coricidin cold and cough) made me feel reality differently like I felt like a midget (or I was 7 feet tall), like gravity was greater than normal, like my head didnt weigh anything, like everything was some terribly lit rip-off tarantino film. You can't sleep when you're coming down and you don't eat for 12hrs to a day because of them. I'll admit sometimes I could get a cool warm feeling buzz from them, and the first couple times I got the whole out of body thing, and that was fresh. They're ok to do a couple of times to maybe learn how your own body handles this sort of thing, and how to handle a trip (the out of body was pretty nuts).