I've not used your exact template because I wasn't able to just copy/paste it into Visual Studio without changing resource names ect. When posting code to fix try and make it completely isolated, makes fixing problems much easier for us :D
The template I've provided below applies a drop shadow effect to the content of a button when the keyboard focus is set, I used Effect instead of BitMapEffect because it's much faster and also BitMapEffect is now obsolete. You might need to tweak the effect parameters to make it glow better.
<Window x:Class="GlowingButton.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Background="WhiteSmoke"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<Style TargetType="Button">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
<Border BorderBrush="Blue" CornerRadius="5" BorderThickness="1">
<ContentPresenter x:Name="test" HorizontalAlignment="Center" VerticalAlignment="Center" Content="{TemplateBinding Content}"/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsKeyboardFocused" Value="True">
<Trigger.Setters>
<Setter TargetName="test" Property="Effect">
<Setter.Value>
<DropShadowEffect Color="Blue" BlurRadius="10" ShadowDepth="0"/>
</Setter.Value>
</Setter>
</Trigger.Setters>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
<Grid>
<Button Margin="100" Content="test" Foreground="Black" FontSize="20"/>
</Grid>
</Window>