Thanks to all for the posts. I, too, tried spray mounting once or twice. IIRC both surfaces had to be sprayed which unless you were doing a bleed mount made the job really fussy, since any overspray on the mount board looked bad. I've discovered that there are foam core boards made by Bainbridge and others with heat activated adhesive. This might be the best solution. No tacking iron, apparently just position the print on the board, cover with a cover sheet (what else?) and press.
I'll get the press Saturday, along with a complete Retina IIIc kit.
Some things just can't be passed up! I'll work up a report.