The tutorial about ironing might have been using washable glue, not 505.
This may sound crazy, but I do my basting standing up. I pin a bedsheet over my design wall, then put up my backing, right side down and spray the top 1/4 of the backing. I position the batting (an extra pair of hands really helps here) and smooth it down, then pull it back up to where it needs to be sprayed. I spray another 1/4 of the backing and smooth, then another 1/4 and smooth, then the last 1/4. Then I repeat with the top, but I pin the top about 1/4 down, then let it fold down and spray the fabric. I was taught not to spray the batting, because you get better adhesion by spraying the flat fabric rather than the bumpy batting. Then I lift / spray / smooth the rest of the top. I do use a pin to mark the center at the top and bottom on the backing, batting and top to try to keep everything centered. Once I have it all sprayed and smoothed, I turn it over and smooth out the backing. I do it this way because I can't get on my knees anymore, and I don't have a flat surface large enough to lay it out on.