what do you use to remove gasket materal and carbon

I just got the head and jugs off my kz305. The base gasket did not come off well. Also carbon inside head and piston tops. Any labor saving chemicals for cleaning?
The reason for the tear down was oil leaking around head gasket and high oil consumption.
Unfortunaly, nothing seemed amiss. Ring gap was well within spec., and valve seals seamed snug around valve stems.

I could be wrong, but I don't there is such a chemical that will lift off old gasket remains.
I keep an old toothbrush and baked beans tin half-filled with petrol at hand. This helps to moisten and clean things, at least. Petrol is cheaper than anything in a can. Edge of a Stanley knife blade to remove baked-in old gasket material while trying my best to not scratch the aluminium, and if it's a situation where grit won't fall into the engine, I will use a fresh, new knife-sharpening block from Ebay to flatten the mating surfaces all out again evenly after this has been done. It's a time-consuming process.
Carbon on piston crowns: brass brush bit on a power drill to get rid (don't apply much force, because the wires on the bit might be brass-coated steel). Inside head: just get it out by any old means, including fingers and sandpaper (while valves are still installed and closed), making sure to not touch the mating surface at all, and wash out all traces of grit when done. 
These methods are what work for me.

Are you sure as to the cause for high oil consumption? Perhaps you have a failing seal elsewhere in the engine.
Also, just to note, some of the old Kawasakis didn't come with a rocker cover gasket. This means that leaving it on the side stand for any length of time will cause an oil leak which looks like it's coming from the head when it's not.

Copper plumbing pipe with a flattened, squared off and sharpened end makes a good scraper that won't damage the aluminium..

After a lot of years, I've settled on this:

Rectangular, scraper-style razor blades, bought in packs of 100. Scraping at an acute angle, and (and this is the part that took me years to figure out) throwing them away as soon as they begin to show a hint of dulling. I go through a ton of them, and they make garbage bags dangerous, but it keeps me from biting into aluminum.

Then a die grinder with a red ScotchBrite pad used flat (not angled) with a very light touch.

I ain't saying it's the only way, but it works well.

For carbon I use bronze or copper brushes with a lot of carb cleaner.  Either that or vapour blasting.

Thanks everyone. But I was really looking for something more magical, quick and easy. I spent the entire day today scraping a base gasket that seemed almost welded to both engine and cylinders. Just a little more to go. I should be able to start reassembly tomorrow.
Should I use any grease or sealent on the new base gasket or just install dry?

If you want anything thats less labour intensive then the suggestions given, then i can recomend vapour blasting, brings everything up like new. Not cheap though, Im in the process of rebuilding my engine at moment, have you checked the exhaust valve guides mine were completely shot, althogh valves themselved ok.
so having them replaced by eng company along with head skim, again not cheap but not cost effective not to do it.
Def worth checking before rebuilding.

I use disposable plastic putty knives from Home Depot. They have an edge as sharp as a razor. A wide one can be split into three or four and they last surprisingly long. They cannot damage the aluminum no matter what and cost under a buck apiece.