I have not found a way to do that, Jim. You can copy an item with a desired style and then select an item you want and click "Paste Style". For words switching between layers, I frequently just copy a word in the style I want and paste it and type over that. Ugly but gets job done.
I start with a blank 3300 x 2550 template with layers set up as follows from bottom to top:
White Background - Easier getting rid of unwanted black - big white rectangle under everything
Layer 1 - Screenshot of GE mapped course.
Street Lines - Tracing of Streets maybe 20 in Black
Street Fill - Copy of Street Lines Change to White Stroke width say 18
Objects - Detail drawings, mile marks, etc.
Course Arrows - Detailed drawing of arrows all in same style
Alpha - all words all in same style.
Swatch of Oscar_11 which I gave to measuring partner/ certifer Dave Rogers who says he now easily gets our maps under 400K in Gimp. AND last couple have been VERY true to my "artistry".
Oscar_11:
GIMP Palette
Name: Oscar 11
Columns: 16#
0 220 0 Green
255 0 255 Magenta
255 255 0 Yellow
65 105 255 Blue
255 127 0 Orange
255 255 255 (white)
0 0 0 (black)
181 37 46 (usatf red)
1 38 57 (usatf blue)
96 96 91 (usatf gray)
142 146 149 (usatf silver)