I have used Permatex® High-Temp Red RTV Silicone Gasket Item # 81160 on exhaust headers with no gasket and on the donuts as well. This was in the automotive shops I have worked in for the past 15 years. While it is said by many a tech that it can mess up an O2 sensor . I learned and did this with older model engines years ago. Also on hotrods where that pesky donut seamed to fail with great success.
http://www.permatex.com/documents/GasketMakerSelector.pdf
My new favorite is Permatex® Ultra Copper® High- Temp RTV Silicone Gasket Maker Item # 81878 Exhaust manifolds/ headers, valve covers, oil pans, timing covers, thermostat housing, water pumps. Temperature Range: -75°F to 700°F intermittent
None of these are hard to clean up. [don't know about the seal all ]
My China motor has no gasket on the intake and has had no air leaks ever. No the gas did not eat it either. The surfaces were perfectly flush is why. I have a copper gasket on the exhaust. A copper or Aluminum gasket on the exhaust will work the best. Yes I delicately butter my exhaust gasket in this stuff.
You make a good point B.W. a simple gasket is all a guy needs to use. My zeal and luck with these products are not necessary to recommend.
All a guy needs is clean surfaces and decent gasket material. If the surfaces are clean and flush conditions are perfect.
I never have tried the said Seal All. I hear its a real mess to clean up. My gasket maker is not.
My personal experience with what I have used has worked for me. I shall avoid the controversy and stop recommending any of this stuff. There is just too much differences in opinion.