If that friend is you yourself, please say it like that... there is nothing self incriminating here anyway. Read our rules.
thnx
Also we can't ultimately decide if you/he/she should or should not do what you propose but normally cannabis and DXM go well together (unlike say alcohol and DXM). And 600 mg can be a bit different from 300 mg. If 300 mg is overwhelming that is a sign of enzyme deficiency meaning that DXM may be a lot more potent miligram per milligram for a person who has that enzyme deficiency than for the average person. Because the DXM cannot be broken down properly in the body. ~10% of caucasian population has this enzyme deficiency which is quite a lot I'd say.
Weed typically does not help to remember the experience - on contrary - so there is that... in my opinion it is more responsible / reasonable to take it easy and try combining with weed at the same dose level as before - 300 - OR upping the dose, but best not at the same time.
Also do it in a safe controllable environment where you can just space out.
Don't overdo it on the weed because overdosing can lead to a lot of anxiety. There is synergy so you probably need less weed than you normally do. But other than that yes weed can help make it a bit more smooth, help avoid nausea, and more such advantages. And lastly: dosing in between 300 mg and 600 mg is also always an option! Say 450 mg, and save higher dose levels for another time.
I don't wish to make this overly complicated for you, but basic questions like these are also fine in the Basic Drug Discussion forum for future reference. Regardless of what type of drug. You can imagine advice on dose and combination with weed is relatively standard.
But don't worry about it this instance.
Word of advice about DXM: make yourself familiar with the things that DXM's very dangerous to combine with like certain anti-depressants and MDMA / XTC.
