I don't seal coat, haven't had a problem, but ET and Rob Macks have lots more experience.
The cloth that is typically used is so loose weave there is no issue with laying out straight, it will still lay completely flat, just pull on the edges until it is flat.
If you do a seal coat, do not let it get hard. Just go ahead and put on the cloth before it hardens.
Any time you let the epoxy completely harden, rinse and scrub with a scotch brite pad. The blush cannot be seen until you cover it with fiberglass or just an epoxy coat when filling, then it looks terrible.
If you decide to sand instead and there is blush, you will fill up the sand paper very rapidly with what looks like wax.
Spend the money for the non-blush hardener. You should still wash if you let a coat completely harden, the epoxy still has a slight chance of blushing, but it is much much less chance.
Keep putting the fill coats on without letting them fully cure. Getting blush in the valleys of the cloth is extremely difficult to get it all out.

Its really not hard. The squeege is your friend especially on the inside.
Don't use too fast of a hardener (depends upon where you are), give yourself a chance to get it all finished without panic.

: Robertl...Thanks for the info....if I do decide to go with the SEAL
: COAT...what about the so called..."AMINE BLUSH"..is
: this a common occurrance or can it be avoided with a lite
: sanding before the fiberglassing?..I also read that if the
: fiberglass is applied before the SEAL COAT is cured you will not
: have to deal with this problem. I got this info out of Nick's
: book....Is this all TRUE?....Just want to make sure of the facts
: and discuss with fellow builders who have gone through the
: experience...before I get started......Thanks....Gordon